Vulnerability-Lookup

UBUNTU-CVE-2026-64846 (CVE-2026-64846)

Vulnerability from osv_ubuntu – Published: 2026-08-20 17:19 – Updated: 2026-09-02 16:22 – Source website

Details

Nix is a package manager for Linux and other Unix systems. Prior to 2.35.0, a malicious derivation executed with the recursive-nix experimental feature can exploit a time-of-check/time-of-use race involving final symlink handling in the LocalStore restore path. The race can cause writeFile to follow a substituted final symlink when opening a path with O_TRUNC instead of enforcing FinalSymlink::DontFollow, allowing the Nix process or nix-daemon to create or truncate an empty file outside the build sandbox with the daemon user's permissions. The primitive does not provide arbitrary-content writes and requires winning the race. This issue is fixed in version 2.35.0.

Severity

2.8 (Low)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-64846	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-64846	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "nix-bin",
            "binary_version": "2.6.0+dfsg-3ubuntu0.1~esm1"
          },
          {
            "binary_name": "nix-setup-systemd",
            "binary_version": "2.6.0+dfsg-3ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "nix",
        "purl": "pkg:deb/ubuntu/nix@2.6.0+dfsg-3ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.3.10+dfsg1-1",
        "2.3.10+dfsg1-1build1",
        "2.6.0+dfsg-2",
        "2.6.0+dfsg-3",
        "2.6.0+dfsg-3ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "nix-bin",
            "binary_version": "2.18.1+dfsg-1ubuntu5+esm2"
          },
          {
            "binary_name": "nix-setup-systemd",
            "binary_version": "2.18.1+dfsg-1ubuntu5+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "nix",
        "purl": "pkg:deb/ubuntu/nix@2.18.1+dfsg-1ubuntu5+esm2?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.16.1+dfsg-3ubuntu1",
        "2.18.1+dfsg-1ubuntu1",
        "2.18.1+dfsg-1ubuntu2",
        "2.18.1+dfsg-1ubuntu4",
        "2.18.1+dfsg-1ubuntu5",
        "2.18.1+dfsg-1ubuntu5+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "nix-bin",
            "binary_version": "2.34.3+dfsg-1"
          },
          {
            "binary_name": "nix-setup-systemd",
            "binary_version": "2.34.3+dfsg-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "nix",
        "purl": "pkg:deb/ubuntu/nix@2.34.3+dfsg-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.26.3+dfsg-1ubuntu4",
        "2.26.3+dfsg-1ubuntu5",
        "2.32.5+dfsg-1ubuntu3",
        "2.32.5+dfsg-2ubuntu1",
        "2.34.3+dfsg-1"
      ]
    }
  ],
  "aliases": [],
  "details": "Nix is a package manager for Linux and other Unix systems. Prior to 2.35.0, a malicious derivation executed with the recursive-nix experimental feature can exploit a time-of-check/time-of-use race involving final symlink handling in the LocalStore restore path. The race can cause writeFile to follow a substituted final symlink when opening a path with O_TRUNC instead of enforcing FinalSymlink::DontFollow, allowing the Nix process or nix-daemon to create or truncate an empty file outside the build sandbox with the daemon user\u0027s permissions. The primitive does not provide arbitrary-content writes and requires winning the race. This issue is fixed in version 2.35.0.",
  "id": "UBUNTU-CVE-2026-64846",
  "modified": "2026-09-02T16:22:32Z",
  "published": "2026-08-20T17:19:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-64846"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-64846"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-64846"
  ]
}

CVE-2026-64846 (GCVE-0-2026-64846)

Vulnerability from cvelistv5 – Published: 2026-08-20 16:18 – Updated: 2026-08-20 19:32

Title

Nix: Arbitrary file truncation outside the sandbox with recursive-nix experimental feature

Summary

Severity

2.8 (Low)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-20 19:32 UTC

CWE

CWE-61 - UNIX Symbolic Link (Symlink) Following
CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/NixOS/nix/security/advisories/…	x_refsource_CONFIRM
https://github.com/NixOS/nix/pull/15401	x_refsource_MISC
https://github.com/NixOS/nix/commit/26679828f74ee…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
NixOS	nix	Affected: < 2.35.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-64846",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-20T19:32:14.918442Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-20T19:32:22.878Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "nix",
          "vendor": "NixOS",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.35.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Nix is a package manager for Linux and other Unix systems. Prior to 2.35.0, a malicious derivation executed with the recursive-nix experimental feature can exploit a time-of-check/time-of-use race involving final symlink handling in the LocalStore restore path. The race can cause writeFile to follow a substituted final symlink when opening a path with O_TRUNC instead of enforcing FinalSymlink::DontFollow, allowing the Nix process or nix-daemon to create or truncate an empty file outside the build sandbox with the daemon user\u0027s permissions. The primitive does not provide arbitrary-content writes and requires winning the race. This issue is fixed in version 2.35.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 2.8,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-61",
              "description": "CWE-61: UNIX Symbolic Link (Symlink) Following",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-367",
              "description": "CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-20T16:18:06.729Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/NixOS/nix/security/advisories/GHSA-6h4g-g5j9-fm5f",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/NixOS/nix/security/advisories/GHSA-6h4g-g5j9-fm5f"
        },
        {
          "name": "https://github.com/NixOS/nix/pull/15401",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/NixOS/nix/pull/15401"
        },
        {
          "name": "https://github.com/NixOS/nix/commit/26679828f74ee6e82a4100904e6361f993ff5390",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/NixOS/nix/commit/26679828f74ee6e82a4100904e6361f993ff5390"
        }
      ],
      "source": {
        "advisory": "GHSA-6h4g-g5j9-fm5f",
        "discovery": "UNKNOWN"
      },
      "title": "Nix: Arbitrary file truncation outside the sandbox with recursive-nix experimental feature"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-64846",
    "datePublished": "2026-08-20T16:18:06.729Z",
    "dateReserved": "2026-07-20T18:31:39.290Z",
    "dateUpdated": "2026-08-20T19:32:22.878Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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UBUNTU-CVE-2026-64846 (CVE-2026-64846)

CVE-2026-64846 (GCVE-0-2026-64846)

Tags

Sightings

Nomenclature

Related by attack behaviour