CVE-2026-39860
Nix sandbox escape: file write via symlink at FOD `.tmp` copy destination
Description
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.
INFO
Published Date :
April 8, 2026, 9:17 p.m.
Last Modified :
April 15, 2026, 4:12 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Nix to version 2.34.5 or later.
- Apply vendor-provided patches or updates.
- Ensure Nix daemon runs with least privilege.
- Review Nix build configurations for security.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-39860.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-39860 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-39860
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-39860 vulnerability anywhere in the article.
-
Daily CyberSecurity
Root Access at Risk: Critical Nix Sandbox Escape Overwrites Sensitive System Files
A severe security vulnerability has been identified in the Nix package manager, a tool celebrated by the Linux and Unix communities for making package management reliable and reproducible. Tracked as ... Read more
-
Daily CyberSecurity
Critical Privilege Escalation in Checkmk: Root Access at Risk
A critical-severity security vulnerability has been identified in the Checkmk monitoring platform, potentially allowing local users to seize full control of the host system. The flaw, tracked as CVE-2 ... Read more
The following table lists the changes that have been made to the
CVE-2026-39860 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 15, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N Added CPE Configuration AND OR *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.18.2 up to (including) 2.18.9 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.19.4 up to (including) 2.19.7 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.20.5 up to (including) 2.20.9 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.21.0 up to (excluding) 2.28.6 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.29.0 up to (excluding) 2.29.3 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.30.0 up to (excluding) 2.30.4 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.31.0 up to (excluding) 2.31.4 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.32.0 up to (excluding) 2.32.7 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.33.0 up to (excluding) 2.33.4 *cpe:2.3:a:nixos:nix:*:*:*:*:*:*:*:* versions from (including) 2.34.0 up to (excluding) 2.34.5 OR cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:* Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/commit/244f3eee0bbc7f11e9b383a15ed7368e2c4becc9 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/commit/4bc5a3510fa3735798f9ed3a2a30a3ea7b32343a Types: Patch Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/commit/7794354a982449927ee7401cdeb573ddd16c4688 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/commit/a3163b9eabb952b4aa96e376dea95ebcca97b31a Types: Patch Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/pull/10178 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/NixOS/nix/security/advisories/GHSA-g3g9-5vj6-r3gj Types: Mitigation, Patch, Vendor Advisory -
New CVE Received by [email protected]
Apr. 08, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V3.1 AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N Added CWE CWE-61 Added Reference https://github.com/NixOS/nix/commit/244f3eee0bbc7f11e9b383a15ed7368e2c4becc9 Added Reference https://github.com/NixOS/nix/commit/4bc5a3510fa3735798f9ed3a2a30a3ea7b32343a Added Reference https://github.com/NixOS/nix/commit/7794354a982449927ee7401cdeb573ddd16c4688 Added Reference https://github.com/NixOS/nix/commit/a3163b9eabb952b4aa96e376dea95ebcca97b31a Added Reference https://github.com/NixOS/nix/pull/10178 Added Reference https://github.com/NixOS/nix/security/advisories/GHSA-g3g9-5vj6-r3gj