Time-of-check Time-of-use (TOCTOU) Race Condition in Util-linux - CVE-2026-78410
Published: September 2, 2026
Vulnerability identifier: #VU146723
CSH Severity: Low
CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-78410
CWE-ID: CWE-367
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to escalate privileges.
The vulnerability exists due to a time-of-check time-of-use race condition in restricted bind and rbind mount source handling in mount(8) when processing fstab-authorized bind mounts with X-mount.owner, X-mount.group, or X-mount.mode options. A local user can replace the authorized source path or a writable ancestor with a symlink to an attacker-selected directory to escalate privileges.
The issue affects SUID-root mount(8) restricted-user configurations where the authorized bind source is under a user-writable ancestor and the same fstab entry enables ownership or mode-changing post-mount hooks.
Affected software
Util-linux
How to mitigate CVE-2026-78410
Install security update from vendor's website.
Util-linux - addressed in versions 2.41.6, 2.42.3