Description

An issue was discovered in Nix before 2.34.7 and Lix before 2.95.2. Unbounded recursion in the NAR (Nix Archive) parser could lead to a stack-to-heap overflow when the parser is run on a coroutine stack. The stack is allocated without a guard page, which means that a stack overflow could overwrite memory on the heap and could allow arbitrary code execution as the Nix daemon (run as root in multi-user installations) if ASLR hardening is bypassed. This can be exploited by all users able to connect to the daemon (e.g., in Nix, this is configurable via the allowed-users setting, defaulting to all users). The fixed versions are 2.34.7, 2.33.6, 2.32.8, 2.31.5, 2.30.5, 2.29.4, and 2.28.7 for Nix (introduced in 2.24.4); and 2.95.2, 2.94.2, and 2.93.4 for Lix (introduced in 2.93.0).

Weaknesses 1

References 5

• discourse.nixos.org https://discourse.nixos.org/t/security-advisory-local-privilege-escalation-in-lix-and-nix/77407
• github.com https://github.com/NixOS/nix/security/advisories/GHSA-vh5x-56v6-4368
• lix.systems https://lix.systems/blog/2026-05-05-lix-unsigned-integer-overflow/
• openwall.com https://www.openwall.com/lists/oss-security/2026/05/04/32
• openwall.com https://www.openwall.com/lists/oss-security/2026/05/04/33

Remediation