What’s Vulnerable › Vulnerabilities

CVE-2026-64846: Nix: Arbitrary file truncation outside the sandbox with recursive-nix experimental feature

• Severity: low (CVSS 2.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-20 · updated 2026-10-18
• Weakness: CWE-61

Description

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.

Affected products

• NixOS Nix: before 2.35.0

References

• https://github.com/NixOS/nix/commit/26679828f74ee6e82a4100904e6361f993ff5390
• https://github.com/NixOS/nix/pull/15401
• https://github.com/NixOS/nix/security/advisories/GHSA-6h4g-g5j9-fm5f

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