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
openEuler
util-linux
libblkid
libfdisk
libmount
libsmartcols
libuuid
python-libmount
util-linux-debuginfo
util-linux-debugsource
util-linux-devel
util-linux-user
uuidd
util-linux-help
python3-libmount
openEuler
util-linux
libblkid
libfdisk
libmount
libsmartcols
libuuid
python-libmount
util-linux-debuginfo
util-linux-debugsource
util-linux-devel
util-linux-user
uuidd
util-linux-help
python3-libmount
How to mitigate CVE-2026-78410
Install security update from vendor's website.
Util-linux - addressed in versions 2.41.6, 2.42.3
util-linux - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libblkid - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libfdisk - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libmount - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libsmartcols - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libuuid - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
python-libmount - update to 2.35.2-35
util-linux-debuginfo - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-debugsource - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-devel - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-user - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
uuidd - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-help - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
python3-libmount - addressed in versions 2.37.2-56, 2.39.1-44
util-linux - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libblkid - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libfdisk - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libmount - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libsmartcols - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
libuuid - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
python-libmount - update to 2.35.2-35
util-linux-debuginfo - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-debugsource - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-devel - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-user - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
uuidd - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
util-linux-help - addressed in versions 2.35.2-35, 2.37.2-56, 2.39.1-44
python3-libmount - addressed in versions 2.37.2-56, 2.39.1-44