Nix allows macOS sandbox escape via built-in builders

published 2024-10-31 2 y ago modified 2026-06-17 4 mo ago also EUVD-2024-45355

cvss: 1.0; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits: 0; none known

Nix is a package manager for Linux and other Unix systems. On macOS, built-in builders (such as `builtin:fetchurl`, exposed to users with `import <nix/fetchurl.nix>`) were not executed in the macOS sandbox. Thus, these builders (which are running under the `nixbld*` users) had read access to world-readable paths and write access to world-writable paths outside of the sandbox. This issue is fixed in 2.18.9, 2.19.7, 2.20.9, 2.21.5, 2.22.4, 2.23.4, and 2.24.10. Note that sandboxing is not enabled by default on macOS. The Nix sandbox is not primarily intended as a security mechanism, but as an aid to improve reproducibility and purity of Nix builds. However, sandboxing *can* mitigate the impact of other security issues by limiting what parts of the host system a build has access to.

Patch / fix

fixed in 1 links 1

nixos nix 2.18.9, 2.20.9, 2.21.5, 2.22.4, 2.23.4, 2.24.10

github.com/NixOS/nix@597fcc9 commit

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 y ago (2024-10-31)

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	1.0	CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
CNA	4.0	1.0	CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

NixOS nix

Classification

Weakness

CWE-693 Protection Mechanism Failure

References

Sources

CVE List CVE-2024-51481
NVD CVE-2024-51481

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary