Time-of-check Time-of-use (TOCTOU) Race Condition in Util-linux - CVE-2026-53612
Published: September 2, 2026
Vulnerability identifier: #VU146718
CSH Severity: Low
CVSS v4: 7.3 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-53612
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 the mount(8) hook_owner.c post-mount hook when performing path-based chmod() and lchown() operations on the mount target after mount() completes. A local user can swap a path component with renameat2(RENAME_EXCHANGE) to escalate privileges.
Exploitation requires an /etc/fstab entry with both user and X-mount.mode=, X-mount.owner=, or X-mount.group= options, and the mount target path must have a writable ancestor directory.
Affected software
Util-linux
openEuler
Fedora
libmount
python3-libmount
util-linux-debuginfo
util-linux-debugsource
util-linux-devel
util-linux-user
uuidd
util-linux-help
util-linux
libblkid
libfdisk
libuuid
libsmartcols
openEuler
Fedora
libmount
python3-libmount
util-linux-debuginfo
util-linux-debugsource
util-linux-devel
util-linux-user
uuidd
util-linux-help
util-linux
libblkid
libfdisk
libuuid
libsmartcols
How to mitigate CVE-2026-53612
Install security update from vendor's website.
Util-linux - addressed in versions 2.41.5, 2.42.2
libmount - update to 2.39.1-44
python3-libmount - update to 2.39.1-44
util-linux-debuginfo - update to 2.39.1-44
util-linux-debugsource - update to 2.39.1-44
util-linux-devel - update to 2.39.1-44
util-linux-user - update to 2.39.1-44
uuidd - update to 2.39.1-44
util-linux-help - update to 2.39.1-44
util-linux - update to 2.39.1-44
libblkid - update to 2.39.1-44
libfdisk - update to 2.39.1-44
libuuid - update to 2.39.1-44
libsmartcols - update to 2.39.1-44
util-linux - addressed in versions 2.41.5-1.fc43, 2.41.5-1.fc44
libmount - update to 2.39.1-44
python3-libmount - update to 2.39.1-44
util-linux-debuginfo - update to 2.39.1-44
util-linux-debugsource - update to 2.39.1-44
util-linux-devel - update to 2.39.1-44
util-linux-user - update to 2.39.1-44
uuidd - update to 2.39.1-44
util-linux-help - update to 2.39.1-44
util-linux - update to 2.39.1-44
libblkid - update to 2.39.1-44
libfdisk - update to 2.39.1-44
libuuid - update to 2.39.1-44
libsmartcols - update to 2.39.1-44
util-linux - addressed in versions 2.41.5-1.fc43, 2.41.5-1.fc44