What’s Vulnerable › Vulnerabilities

CVE-2026-53612: util-linux mount hook_owner TOCTOU allows local privilege escalation

• Severity: high (CVSS 7.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-14 · updated 2026-10-16
• Weakness: CWE-367

Description

util-linux is a random collection of Linux utilities. In util-linux 2.39 through 2.41.4 and 2.42 through 2.42.1, the SUID `mount` utility's `hook_owner.c` post-mount hook performs path-based `chmod()` and `lchown()` operations on a previously validated mount target. A local low-privileged user authorized by an `/etc/fstab` entry with `user` or `users` and an `X-mount.mode`, `X-mount.owner`, or `X-mount.group` option can use `renameat2(RENAME_EXCHANGE)` to race a writable ancestor of the target and redirect the privileged ownership or mode change to a root-owned path, potentially gaining root privileges. This issue is fixed in 2.41.5 and 2.42.2.

Affected products

• util-linux: from 2.39, < 2.41.5; from 2.42, < 2.42.2

References

• https://github.com/util-linux/util-linux/commit/24da33905c7115c4cbccd0afb2a469804e96467a
• https://github.com/util-linux/util-linux/commit/722c96974dd4009a334e4aee556eedaab5fb94b4
• https://github.com/util-linux/util-linux/commit/897a08c2b11dfa66975c3d24d63c7bf5f5be1a7c
• https://github.com/util-linux/util-linux/commit/d0c5adaeb3a3d823aba1377794de8f009b8152cc
• https://github.com/util-linux/util-linux/releases/tag/v2.41.5
• https://github.com/util-linux/util-linux/releases/tag/v2.42.2
• https://github.com/util-linux/util-linux/security/advisories/GHSA-g8wm-75wr-g2vh
• https://github.com/util-linux/util-linux/security/advisories/GHSA-g8wm-75wr-g2vh

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