CVE-2021-27851

NameCVE-2021-27851
DescriptionA 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
Debian Bugs985467

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
guix (PTS)bullseye1.2.0-4fixed
sid1.3.0-5fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
guixsource(unstable)1.2.0-4unimportant985467

Notes

https://issues.guix.gnu.org/47229
https://git.savannah.gnu.org/cgit/guix.git/commit/?id=ec7fb669945bfb47c5e1fdf7de3a5d07f7002ccf
https://guix.gnu.org/en/blog/2021/risk-of-local-privilege-escalation-via-guix-daemon/
Neutralised by kernel hardening (fs.protected_hardlinks = 1)

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