Vulnerability in Linux Nixos (CVE-2026-39860)
Summary
Vulnerability in Linux Nixos (CVE-2026-39860). Confidential information can be exposed externally. Mitigation: upgrade to 2.34.5 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-39860 has been found in Linux Nixos.
Confidential information can be exposed externally. CVSS score: 9.0/10.
What to do: upgrade Linux Nixos to 2.34.5 or later.
If unsure, ask your IT team or search "Linux Nixos CVE-2026-39860" on the vendor's site.
CVE-2026-39860 (Linux Nixos) — CWE-61 / CVSS v3 9.0
Attack vector: local / unauthenticated / no user interaction
Patched: 2.34.5 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-61) exists in Linux Nixos.
Check the vendor advisory for the affected versions of Linux Nixos.
Severity: Critical (CVSS 9.0/10). Confidential information can be exposed externally.
Update to 2.34.5.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Nixos' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'Nixos' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Nixosを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade Linux Nixos to 2.34.5ステージング環境で 2.34.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-39860 nix
- Ubuntu UBUNTU-CVE-2026-39860 nix