NixOS nix up to 2.34.4 on Linux symlink

Summaryinfo

A vulnerability marked as critical has been reported in NixOS nix up to 2.34.4 on Linux. Affected is an unknown function. The manipulation leads to symlink. This vulnerability is referenced as CVE-2026-39860. The attack can only be performed from a local environment. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in NixOS nix up to 2.34.4 on Linux. This issue affects an unknown code. The manipulation with an unknown input leads to a symlink vulnerability. Using CWE to declare the problem leads to CWE-61. The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Nix is a package manager for Linux and other Unix systems. A bug in the fix for CVE-2024-27297 allowed for arbitrary overwrites of files writable by the Nix process orchestrating the builds (typically the Nix daemon running as root in multi-user installations) by following symlinks during fixed-output derivation output registration. This affects sandboxed Linux builds - sandboxed macOS builds are unaffected. The location of the temporary output used for the output copy was located inside the build chroot. A symlink, pointing to an arbitrary location in the filesystem, could be created by the derivation builder at that path. During output registration, the Nix process (running in the host mount namespace) would follow that symlink and overwrite the destination with the derivation's output contents. In multi-user installations, this allows all users able to submit builds to the Nix daemon (allowed-users - defaulting to all users) to gain root privileges by modifying sensitive files. This vulnerability is fixed in 2.34.5, 2.33.4, 2.32.7, 2.31.4, 2.30.4, 2.29.3, and 2.28.6.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-39860 since 04/07/2026. The exploitation is known to be easy. An attack has to be approached locally. Neither technical details nor an exploit are publicly available.

Upgrading to version 2.28.6, 2.29.3, 2.30.4, 2.31.4, 2.32.7, 2.33.4 or 2.34.5 eliminates this vulnerability. Applying the patch 244f3eee0bbc7f11e9b383a15ed7368e2c4becc9 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• NixOS

Name

• nix

Version

• 2.18.0
• 2.18.1
• 2.18.2
• 2.18.3
• 2.18.4
• 2.18.5
• 2.18.6
• 2.18.7
• 2.18.8
• 2.18.9
• 2.19.0
• 2.19.1
• 2.19.2
• 2.19.3
• 2.19.4
• 2.19.5
• 2.19.6
• 2.19.7
• 2.20.0
• 2.20.1
• 2.20.2
• 2.20.3
• 2.20.4
• 2.20.5
• 2.20.6
• 2.20.7
• 2.20.8
• 2.20.9
• 2.28.0
• 2.28.1
• 2.28.2
• 2.28.3
• 2.28.4
• 2.28.5
• 2.29.0
• 2.29.1
• 2.29.2
• 2.30.0
• 2.30.1
• 2.30.2
• 2.30.3
• 2.31.0
• 2.31.1
• 2.31.2
• 2.31.3
• 2.32.0
• 2.32.1
• 2.32.2
• 2.32.3
• 2.32.4
• 2.32.5
• 2.32.6
• 2.33.0
• 2.33.1
• 2.33.2
• 2.33.3
• 2.34.0
• 2.34.1
• 2.34.2
• 2.34.3
• 2.34.4

License

• open-source

Website

• Product: https://github.com/NixOS/nix/

CPE 2.3info

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CPE 2.2info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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