CVE-2021-27851
Publication date 26 April 2021
Last updated 26 August 2025
Ubuntu priority
Description
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| guix | 26.04 LTS resolute | Not in release |
| 24.04 LTS noble |
Not affected
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal | Not in release | |
| 18.04 LTS bionic | Not in release | |
| 16.04 LTS xenial | Not in release | |
| 14.04 LTS trusty | Not in release |
Severity score breakdown
CVSS version: CVSS v3.0
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