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NixApplication · Nixos

CVE-2026-39860

HIGH · 8.4 CVSS v3.1 Published 2026-04-08
Fix available
A fix is available. Upgrade to 2.28.6 / 2.29.3 or later.
See remediation →
86/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NixApplication
Affected:>= 2.18.2, <= 2.18.9>= 2.19.4, <= 2.19.7>= 2.20.5, <= 2.20.9>= 2.21.0, < 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

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.28.6 / 2.29.3 / 2.30.4 or later
Fixed in 2.28.62.29.32.30.4
Vendor patch github.com →
Recommended fix High confidence

Upgrade to Nix 2.28.6 or later (or the latest version in your current branch: 2.34.5, 2.33.4, 2.32.7, 2.31.4, 2.30.4, 2.29.3, or 2.28.6)

  1. 1. Identify the currently installed Nix version using: nix --version
  2. 2. Based on your current version branch, upgrade to the corresponding fixed release:
  3. - If using Nix 2.18.x: upgrade to 2.18.10 or later (or 2.28.6, 2.29.3, 2.30.4, etc.)
  4. - If using Nix 2.19.x: upgrade to 2.19.8 or later (or 2.28.6, 2.29.3, 2.30.4, etc.)
  5. - If using Nix 2.20.x: upgrade to 2.20.10 or later (or 2.28.6, 2.29.3, 2.30.4, etc.)
  6. - If using Nix 2.21.x through 2.27.x: upgrade to 2.28.6 or later
  7. 3. In multi-user installations, ensure allowed-users configuration is restricted to only trusted users until the upgrade is complete
  8. 4. Verify the upgrade was successful by running: nix --version
Caveat Minor: This is a security patch release; no breaking changes expected for typical usage

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-39860 in production — separate from our analysis above.

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