Vulnerability in GNU Guix
CVE-2021-27851
A security vulnerability that can lead to local privilege escalation has been found in ’guix-daemon’. It affects multi-user setups in which ’guix-daemon’ runs locally. The attack consists in having an unprivileged user spawn a build process, for instance with `guix build`, that makes its build directory world-writable. The user then creates a hardlink to a root-owned file such as /etc/shadow in that build directory. If the user passed the --keep-failed option and the build eventually fails, the daemon changes ownership of the whole build tree, including the hardlink, to the user. At that point, the user has write access to the target file. Versions after and including v0.11.0-3298-g2608e40988, and versions prior to v1.2.0-75109-g94f0312546 are vulnerable.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (24.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 24.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- GNU Guix
- GNU Guix Guix-Daemon — versions v0.11.0-3298-g2608e40988, unspecified
Weakness classification (CWE)
References
- guix.gnu.org/en/blog/2021/risk-of-local-privilege-escalation-via-guix-daemon/ (Patch, Vendor Advisory)
- bugs.gnu.org/47229 (Patch, Mailing List, Issue Tracking, Vendor Advisory)
Frequently asked questions
- What is CVE-2021-27851?
- CVE-2021-27851 is a medium-severity vulnerability in GNU Guix, classified under CWE-264. CVSS score: 5.5/10. Published 2021-04-26.
- How severe is CVE-2021-27851?
- Medium severity. CVSS v3 base score is 5.5 out of 10.