{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.3.4",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "adr-viewer",
        "purl": "pkg:brew/adr-viewer"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.3.0"
            },
            {
              "fixed": "1.4.0_6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.3.4",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.3.4"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-adr-viewer-CVE-2026-59930",
  "modified": "2026-09-18T14:56:30Z",
  "published": "2026-08-13T16:35:11Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.3.4",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "buku",
        "purl": "pkg:brew/buku"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.1"
            },
            {
              "fixed": "5.1_6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.3.4",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.3.4"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-buku-CVE-2026-59930",
  "modified": "2026-09-18T15:06:13Z",
  "published": "2026-08-13T16:38:25Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.3.3",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "iredis",
        "purl": "pkg:brew/iredis"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.9.4"
            },
            {
              "fixed": "1.16.1_3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.3.3",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.3.3"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-iredis-CVE-2026-59930",
  "modified": "2026-09-17T17:45:16Z",
  "published": "2026-08-13T17:00:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.3.4",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "jiratui",
        "purl": "pkg:brew/jiratui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.8.0"
            },
            {
              "fixed": "1.10.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.3.4",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.3.4"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-jiratui-CVE-2026-59930",
  "modified": "2026-09-17T18:51:24Z",
  "published": "2026-08-13T17:00:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.3.4",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "jupyterlab",
        "purl": "pkg:brew/jupyterlab"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.2.0"
            },
            {
              "fixed": "4.6.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.3.4",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.3.4"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-jupyterlab-CVE-2026-59930",
  "modified": "2026-09-17T19:02:18Z",
  "published": "2026-08-13T17:01:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "mistune",
        "resource_purl": "pkg:pypi/mistune@3.1.4",
        "upstream_fixed_in": "3.3.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "recon-ng",
        "purl": "pkg:brew/recon-ng"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/mistune@3.1.4",
        "name": "mistune",
        "resource": "mistune",
        "strategy": "registry",
        "subject_version": "3.1.4"
      }
    ]
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "BREW-recon-ng-CVE-2026-59930",
  "modified": "2026-09-10T01:05:54Z",
  "published": "2026-08-13T17:32:25Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content",
  "upstream": [
    "GHSA-2hm2-hc3v-44h9",
    "CVE-2026-59930",
    "PYSEC-2026-2218"
  ]
}

{
  "assigner": "ENISA",
  "date_reserved": "2026-10-02T07:51:24.618000+00:00",
  "id": "EUVD-2026-335303"
}

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "mistune",
          "vendor": "lepture",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.3.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "63E1B933-D2E2-44EF-A56C-94483300845B",
              "versionEndExcluding": "3.3.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable toc_N values without slugifying the heading text, allowing attacker-controlled id=\"toc_N\" content to collide with generated anchors and redirect same-page navigation, CSS selectors, or JavaScript handlers. This issue is fixed in version 3.3.0."
    }
  ],
  "id": "CVE-2026-59930",
  "lastModified": "2026-07-09T19:28:30.570",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 4.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-59930",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-09T13:53:53.247241Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T17:17:28.867",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-345"
        },
        {
          "lang": "en",
          "value": "CWE-1284"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59930"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1284",
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:35:11Z",
    "nvd_published_at": "2026-07-08T17:17:28Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\n**Type:** Predictable identifier generation. The `toc` plugin and `TableOfContents` directive both default to generating heading IDs of the form `toc_1`, `toc_2`, `toc_3`, ... with no input-derived component. An attacker who can place a heading anywhere in the document can predict which `toc_N` ID it will receive, and can inject HTML elsewhere (in a non-heading context) that uses the same `id=\"toc_N\"` to either (a) shadow the legitimate heading anchor, breaking same-page navigation, or (b) collide with CSS or JavaScript that targets `#toc_N` selectors, redirecting click handlers and styling to attacker-chosen content.\n**File:** `src/mistune/toc.py` line 36-37 (`heading_id = lambda token, index: \"toc_\" + str(index + 1)`); `src/mistune/directives/toc.py` line 33 (same default).\n**Root cause:** the default `heading_id` callback ignores the heading\u0027s text content and uses only the headings\u0027s order in the document. Two documents rendered together (or one document with attacker-influenced headings spliced into trusted content) produce overlapping `toc_N` IDs. Because `id` attribute uniqueness is required by HTML, browsers behaviour on duplicate IDs is undefined; `document.getElementById(\u0027toc_1\u0027)` returns the first match, `getElementsByTagName + querySelector` semantics differ across paths, and CSS rules targeting `#toc_1` apply to whichever element matches first in tree order.\n\n## Affected Code\n\n**File:** `src/mistune/toc.py`, lines 33-39.\n\n```python\ndef add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n    if heading_id is None:\n        def heading_id(token, index):\n            return \"toc_\" + str(index + 1)               # \u003c-- BUG: index-only ID, no slug derived from heading text\n```\n\n**File:** `src/mistune/directives/toc.py`, lines 32-33.\n\n```python\nclass TableOfContents(DirectivePlugin):\n    def __init__(self, min_level=1, max_level=3):\n        # ...\n\n    def generate_heading_id(self, token, index):\n        return \"toc_\" + str(index + 1)                   # \u003c-- BUG: same predictable scheme\n```\n\n**Why it\u0027s wrong:** the standard markdown-engine convention (used by GitHub-flavoured Markdown, Sphinx, MkDocs, pandoc, every modern markdown renderer in production) is to slugify the heading TEXT for the ID \u2014 `\u003ch1 id=\"introduction\"\u003eIntroduction\u003c/h1\u003e` \u2014 with a numeric suffix appended only when slug collisions occur. mistune\u0027s default punts the slugification entirely and produces purely positional IDs that an attacker can predict in O(1).\n\nThe downstream impacts:\n- Same-page links with `[click](#toc_1)` go to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker can land any HTML element with `id=\"toc_1\"` before the real heading (via inline_html with `escape=False`, via the include-directive HTML branch, via attacker-supplied content earlier in the document), navigation is hijacked.\n- CSS rules targeting `#toc_1` apply to the wrong element.\n- JavaScript bound to `document.getElementById(\u0027toc_1\u0027)` operates on the wrong element.\n- The TOC\u0027s own `\u003ca href=\"#toc_1\"\u003e` link in the rendered TOC list points to whichever element wins the duplicate-ID race.\n\n## Exploit Chain\n\n1. Application uses mistune with `add_toc_hook(md)` or `TableOfContents` directive enabled (the documented setup for sites with TOC support).\n2. Application renders an attacker-supplied document, or splices attacker content into a trusted document. With `escape=False` (or via the include-directive `.html` branch covered by my prior advisory), the attacker can place `\u003ca id=\"toc_1\"\u003e...\u003c/a\u003e` anywhere in the document.\n3. mistune assigns `id=\"toc_1\"` to the first heading. Now there are two elements with `id=\"toc_1\"` in the page.\n4. The rendered TOC contains `\u003ca href=\"#toc_1\"\u003eFirst heading\u003c/a\u003e`. Clicking it navigates to whichever element with `id=\"toc_1\"` appears first in tree order. If the attacker placed their `\u003ca id=\"toc_1\"\u003e` BEFORE the heading, navigation is hijacked.\n5. Same-page CSS / JS / aria-described references to `#toc_1` similarly redirect.\n\n## Security Impact\n\n**Severity:** sec-low. Not a direct XSS or RCE; the issue is identifier confusion that enables UI-redirection / navigation-hijack attacks. The realistic attacker capability is \"make an internal anchor link go to attacker content instead of the real heading\", or \"make a CSS selector apply to attacker content\", or \"break aria/screen-reader associations\".\n**Attacker capability:** with the ability to plant any HTML element with `id=\"toc_N\"` in the document, hijack `\u003ca href=\"#toc_N\"\u003e` navigation and any CSS/JS targeting that ID. With `escape=False`, this is straightforward. With `escape=True`, the attacker needs another vector to land a raw `id` attribute (one of the include-directive branches, a sibling tooling pipeline that lets HTML through, etc.).\n**Preconditions:** application uses TOC + the default `heading_id` callback. If the application provides its own `heading_id` (e.g., one based on slugified heading text, with collision suffixes), this finding does not apply.\n**Differential:** PoC-verified against mistune@3.2.1:\n\n```python\nimport mistune\nfrom mistune.directives import RSTDirective, TableOfContents\nmd = mistune.create_markdown(plugins=[RSTDirective([TableOfContents()])])\n\nprint(md(\u0027\u0027\u0027\n.. toc::\n\n# Heading 1\n\n# Heading 2\n\u0027\u0027\u0027))\n\n# Output (note: id=\"toc_1\" / id=\"toc_2\", purely positional):\n# \u003cdetails class=\"toc\" open\u003e\n#   \u003csummary\u003eTable of Contents\u003c/summary\u003e\n#   \u003cul\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_1\"\u003eHeading 1\u003c/a\u003e\u003c/li\u003e\n#     \u003cli\u003e\u003ca href=\"#toc_2\"\u003eHeading 2\u003c/a\u003e\u003c/li\u003e\n#   \u003c/ul\u003e\n# \u003c/details\u003e\n# \u003ch1 id=\"toc_1\"\u003eHeading 1\u003c/h1\u003e\n# \u003ch1 id=\"toc_2\"\u003eHeading 2\u003c/h1\u003e\n```\n\nThe patched build (with the suggested fix below) produces text-derived slugs like `id=\"heading-1\"` and `id=\"heading-2\"`, which are tied to content rather than position.\n\n## Suggested Fix\n\nDefault to slugifying the heading text:\n\n```diff\n--- a/src/mistune/toc.py\n+++ b/src/mistune/toc.py\n@@ -33,9 +33,18 @@ def add_toc_hook(md, min_level=1, max_level=3, heading_id=None):\n     if heading_id is None:\n+        import re\n+        _slug_re = re.compile(r\"[^a-z0-9]+\")\n+        seen = {}\n         def heading_id(token, index):\n-            return \"toc_\" + str(index + 1)\n+            text = striptags(md.renderer(md.inline(token[\"text\"], {}), BlockState()))\n+            slug = _slug_re.sub(\"-\", text.lower()).strip(\"-\") or \"section\"\n+            n = seen.get(slug, 0)\n+            seen[slug] = n + 1\n+            return slug if n == 0 else f\"{slug}-{n}\"\n```\n\nSame change applies to `src/mistune/directives/toc.py:33`. Existing applications that have hardcoded `#toc_N` anchors will break; document the migration in the changelog and consider providing an opt-out flag for the legacy behaviour. Add a regression test that asserts heading IDs are slug-derived, not position-derived, and that collisions get a `-N` suffix.",
  "id": "GHSA-2hm2-hc3v-44h9",
  "modified": "2026-07-20T21:35:12Z",
  "published": "2026-07-20T21:35:11Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59930"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2218.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id=\"toc_N\"` content"
}