Vulnerability-Lookup

GHSA-86M8-88FQ-XFXP

Vulnerability from github – Published: 2026-05-29 16:50 – Updated: 2026-05-29 16:50

Summary

Gotenberg has an SSRF deny-list bypass in IsPublicIP via IPv6 6to4 / NAT64 / site-local prefixes

Details

Summary

IsPublicIP in pkg/gotenberg/outbound.go incorrectly classifies IPv6 6to4 / NAT64 / deprecated site-local addresses as public IPs, allowing an unauthenticated attacker to reach internal destinations (e.g., cloud metadata services at 169.254.169.254) via a single crafted DNS AAAA record. This is a variant of CVE-2026-44430 (modelcontextprotocol/registry).

Details

IsPublicIP uses Go stdlib helpers (IsLoopback, IsPrivate, IsLinkLocalUnicast, etc.) to block internal IPs. However, these helpers do not recognize IPv6 prefixes that embed IPv4 addresses:

Prefix	RFC	Tunnels to
`2002::/16`	RFC 3056 (6to4)	IPv4 in bits 16-47
`64:ff9b::/96`	RFC 6052 (NAT64 well-known)	IPv4 in low 32 bits
`64:ff9b:1::/48`	RFC 8215 (NAT64 local-use)	IPv4 in low 32 bits
`fec0::/10`	RFC 3879 (deprecated site-local)	internal routing

addr.Unmap() only handles ::ffff:0:0/96 (IPv4-mapped) and has no effect on these prefixes. On dual-stack or NAT64-enabled cloud hosts, the OS kernel transparently routes these addresses to their embedded internal IPv4 destinations.

Vulnerable code (pkg/gotenberg/outbound.go L53-69, commit 93d0103):

func IsPublicIP(addr netip.Addr) bool {
    addr = addr.Unmap() // only handles ::ffff:x.x.x.x
    switch {
    case addr.IsLoopback(), addr.IsPrivate(),
         addr.IsLinkLocalUnicast(), ...:
        return false
    }
    return true // 6to4/NAT64/site-local incorrectly reaches here
}

PoC

cd poc/
./build.sh   # docker build (~30s)
./run.sh     # docker run — exits with code 1 (bug detected)

Expected output: IsPublicIP(2002:a9fe:a9fe::) = true — the function returns true for 3 addresses that wrap 169.254.169.254 (AWS IMDS). Full test file available via GHSA private comment on request.

Impact

An unauthenticated attacker controlling a DNS AAAA record can tunnel gotenberg's outbound HTTP client to AWS/GCP/Azure IMDS (169.254.169.254), leaking IAM credentials. The Chromium URL convert route returns the full response as a PDF (full-read SSRF). Affects all deployments with WithDenyPrivateIPs(true) on dual-stack or NAT64-enabled hosts.

Suggested Fix

Add explicit prefix checks after addr.Unmap():

var blockedIPv6Prefixes = []netip.Prefix{
    netip.MustParsePrefix("2002::/16"),
    netip.MustParsePrefix("64:ff9b::/96"),
    netip.MustParsePrefix("64:ff9b:1::/48"),
    netip.MustParsePrefix("fec0::/10"),
}
for _, p := range blockedIPv6Prefixes {
    if p.Contains(addr) { return false }
}

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gotenberg/gotenberg/v8"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "8.32.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45741"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184",
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-29T16:50:37Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\n`IsPublicIP` in `pkg/gotenberg/outbound.go` incorrectly classifies IPv6 6to4 / NAT64 / deprecated site-local addresses as public IPs, allowing an unauthenticated attacker to reach internal destinations (e.g., cloud metadata services at `169.254.169.254`) via a single crafted DNS AAAA record. This is a variant of CVE-2026-44430 (modelcontextprotocol/registry).\n\n### Details\n\n`IsPublicIP` uses Go stdlib helpers (`IsLoopback`, `IsPrivate`, `IsLinkLocalUnicast`, etc.) to block internal IPs. However, these helpers do not recognize IPv6 prefixes that embed IPv4 addresses:\n\n| Prefix | RFC | Tunnels to |\n|--------|-----|-----------|\n| `2002::/16` | RFC 3056 (6to4) | IPv4 in bits 16-47 |\n| `64:ff9b::/96` | RFC 6052 (NAT64 well-known) | IPv4 in low 32 bits |\n| `64:ff9b:1::/48` | RFC 8215 (NAT64 local-use) | IPv4 in low 32 bits |\n| `fec0::/10` | RFC 3879 (deprecated site-local) | internal routing |\n\n`addr.Unmap()` only handles `::ffff:0:0/96` (IPv4-mapped) and has no effect on these prefixes. On dual-stack or NAT64-enabled cloud hosts, the OS kernel transparently routes these addresses to their embedded internal IPv4 destinations.\n\nVulnerable code (`pkg/gotenberg/outbound.go` L53-69, commit `93d0103`):\n\n```go\nfunc IsPublicIP(addr netip.Addr) bool {\n    addr = addr.Unmap() // only handles ::ffff:x.x.x.x\n    switch {\n    case addr.IsLoopback(), addr.IsPrivate(),\n         addr.IsLinkLocalUnicast(), ...:\n        return false\n    }\n    return true // 6to4/NAT64/site-local incorrectly reaches here\n}\n```\n\n### PoC\n```\ncd poc/\n./build.sh   # docker build (~30s)\n./run.sh     # docker run \u2014 exits with code 1 (bug detected)\n```\n\nExpected output: `IsPublicIP(2002:a9fe:a9fe::) = true` \u2014 the function returns true for 3 addresses that wrap 169.254.169.254 (AWS IMDS). Full test file available via GHSA private comment on request.\n\n### Impact\n\nAn unauthenticated attacker controlling a DNS AAAA record can tunnel gotenberg\u0027s outbound HTTP client to AWS/GCP/Azure IMDS (169.254.169.254), leaking IAM credentials. The Chromium URL convert route returns the full response as a PDF (full-read SSRF). Affects all deployments with `WithDenyPrivateIPs(true)` on dual-stack or NAT64-enabled hosts.\n\n### Suggested Fix\n\nAdd explicit prefix checks after `addr.Unmap()`:\n```\nvar blockedIPv6Prefixes = []netip.Prefix{\n    netip.MustParsePrefix(\"2002::/16\"),\n    netip.MustParsePrefix(\"64:ff9b::/96\"),\n    netip.MustParsePrefix(\"64:ff9b:1::/48\"),\n    netip.MustParsePrefix(\"fec0::/10\"),\n}\nfor _, p := range blockedIPv6Prefixes {\n    if p.Contains(addr) { return false }\n}\n```",
  "id": "GHSA-86m8-88fq-xfxp",
  "modified": "2026-05-29T16:50:37Z",
  "published": "2026-05-29T16:50:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-86m8-88fq-xfxp"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gotenberg/gotenberg"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Gotenberg has an SSRF deny-list bypass in IsPublicIP via IPv6 6to4 / NAT64 / site-local prefixes"
}

CVE-2026-45741 (GCVE-0-2026-45741)

Vulnerability from cvelistv5 – Published: 2026-08-19 14:32 – Updated: 2026-08-19 18:41

Title

Gotenberg: SSRF deny-list bypass in IsPublicIP via IPv6 6to4 / NAT64 / site-local prefixes

Summary

Gotenberg is a Docker-powered stateless API for PDF files. In 8.32.0 and earlier, the IsPublicIP function in pkg/gotenberg/outbound.go does not reject the 2002::/16 6to4 prefix, the 64:ff9b::/96 and 64:ff9b:1::/48 NAT64 prefixes, the fec0::/10 deprecated site-local prefix, Teredo, and other transition prefixes that can embed or route to non-public IPv4 destinations. The addr.Unmap operation only handles IPv4-mapped IPv6 addresses, so a crafted DNS AAAA record can cause the outbound HTTP client to treat an address wrapping an internal destination such as 169.254.169.254 as public. An unauthenticated attacker can use a conversion route with WithDenyPrivateIPs enabled to reach cloud metadata services, and the Chromium URL conversion route can return the internal response as a PDF, potentially exposing cloud credentials. Exploitation requires a deployment whose host routes the relevant IPv6 prefix, such as a dual-stack or NAT64-enabled environment. This issue is fixed in version 8.33.0.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-19 18:41 UTC

CWE

CWE-184 - Incomplete List of Disallowed Inputs
CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/gotenberg/gotenberg/security/a…	x_refsource_CONFIRM
https://github.com/gotenberg/gotenberg/commit/f9a…	x_refsource_MISC
https://github.com/gotenberg/gotenberg/releases/t…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
gotenberg	gotenberg	Affected: < 8.33.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-45741",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-19T18:41:11.311035Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-19T18:41:18.075Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-86m8-88fq-xfxp"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "gotenberg",
          "vendor": "gotenberg",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 8.33.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Gotenberg is a Docker-powered stateless API for PDF files. In 8.32.0 and earlier, the IsPublicIP function in pkg/gotenberg/outbound.go does not reject the 2002::/16 6to4 prefix, the 64:ff9b::/96 and 64:ff9b:1::/48 NAT64 prefixes, the fec0::/10 deprecated site-local prefix, Teredo, and other transition prefixes that can embed or route to non-public IPv4 destinations. The addr.Unmap operation only handles IPv4-mapped IPv6 addresses, so a crafted DNS AAAA record can cause the outbound HTTP client to treat an address wrapping an internal destination such as 169.254.169.254 as public. An unauthenticated attacker can use a conversion route with WithDenyPrivateIPs enabled to reach cloud metadata services, and the Chromium URL conversion route can return the internal response as a PDF, potentially exposing cloud credentials. Exploitation requires a deployment whose host routes the relevant IPv6 prefix, such as a dual-stack or NAT64-enabled environment. This issue is fixed in version 8.33.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-184",
              "description": "CWE-184: Incomplete List of Disallowed Inputs",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T14:32:50.229Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-86m8-88fq-xfxp",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/gotenberg/gotenberg/security/advisories/GHSA-86m8-88fq-xfxp"
        },
        {
          "name": "https://github.com/gotenberg/gotenberg/commit/f9a01c9fb308372170ab7fc97b17a118ee8a125c",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gotenberg/gotenberg/commit/f9a01c9fb308372170ab7fc97b17a118ee8a125c"
        },
        {
          "name": "https://github.com/gotenberg/gotenberg/releases/tag/v8.33.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gotenberg/gotenberg/releases/tag/v8.33.0"
        }
      ],
      "source": {
        "advisory": "GHSA-86m8-88fq-xfxp",
        "discovery": "UNKNOWN"
      },
      "title": "Gotenberg: SSRF deny-list bypass in IsPublicIP via IPv6 6to4 / NAT64 / site-local prefixes"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-45741",
    "datePublished": "2026-08-19T14:32:50.229Z",
    "dateReserved": "2026-05-13T06:54:34.220Z",
    "dateUpdated": "2026-08-19T18:41:18.075Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

GHSA-86M8-88FQ-XFXP

Summary

Details

PoC

Impact

Suggested Fix

CVE-2026-45741 (GCVE-0-2026-45741)

Tags

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