CVE-2021-27851: gnu guix guix-daemon

Vulnerability summary

CVE-2021-27851 is a medium (CVSS 5.5) vulnerability in gnu guix guix-daemon. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 25.5% of scored vulnerabilities.

Timeline

1. 26-04-2021
   PublishedVulnerability first disclosed.
2. 17-09-2024
   Last modifiedVulnerability information updated.

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.

• CWE-264Permissions, Privileges, and Access ControlsWeaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.
• CWE-59Improper Link Resolution Before File Access ('Link Following')The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.