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VulnerabilityPublished

CVE-2026-39860: NixOS nix · UNIX Symbolic Link (Symlink) Following

Affects NixOS nixSource CVE Database V5

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Mentioned vulnerabilities

Not known to be exploited · CVSS 9.0 Critical · fixed in 2.34.5 : patch NixOS nix as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.0Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.34.5, 2.33.4, 2.32.7 +5
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
NixOSnixAffected
  • >=2.21 <2.28.6
  • >=2.29.0 <2.29.3
  • >=2.30.0 <2.30.4
  • >=2.31.0 <2.31.4
  • >=2.32.0 <2.32.7
  • >=2.33.0 <2.33.4
  • >=2.34.0 <2.34.5
  • >=2.20.5 <=2.20.9
  • >=2.19.4 <=2.19.7
  • >=2.18.2 <=2.18.9
Fixed in
  • 2.34.5
  • 2.33.4
  • 2.32.7
  • 2.31.4
  • 2.30.4
  • 2.29.3
  • 2.28.6
GitHubnixos/nixpkg:github/nixos/nixOther threatsAffected
  • <2.28.6
  • <2.29
Fixed in
  • 2.28.6
  • 2.29

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this vulnerability is available in Nix versions 2.28.6, 2.29.3, 2.30.4, 2.31.4, 2.32.7, 2.33.4, and 2.34.5. Users should upgrade to one of these versions to remediate the issue. There is no vendor advisory content indicating alternative mitigations or that no action is required. Patch status is confirmed by the provided version information. Users running affected versions should prioritize updating to a fixed release to prevent exploitation.

Description

CVE-2026-39860 is a critical vulnerability in the Nix package manager affecting Linux sandboxed builds. It arises from a flaw in the fix for a previous vulnerability (CVE-2024-27297) that allows arbitrary file overwrites by following symbolic links during fixed-output derivation output registration. This can be exploited by users who can submit builds to the Nix daemon, potentially leading to root privilege escalation by overwriting sensitive files. The issue does not affect sandboxed macOS builds. Multiple versions of Nix prior to specific fixed releases are vulnerable. The vulnerability has a CVSS score of 9. A fix is available in Nix versions 2.28.6, 2.29.

References

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