Link following in Util-linux - CVE-2026-78409
Published: September 2, 2026
Vulnerability identifier: #VU146722
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-2026-78409
CWE-ID: CWE-59
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to expose host paths at an fstab-authorized mountpoint.
The vulnerability exists due to improper link resolution before file access in libmount X-mount.subdir detached-tree resolution when processing restricted-user X-mount.subdir paths with open_tree(). A local user can supply a crafted subdirectory path containing intermediate symlinks or procfs paths to expose host paths at an fstab-authorized mountpoint.
Exploitation requires a SUID-root mount(8) configuration that permits unprivileged users to perform fstab-authorized mounts with X-mount.subdir on Linux systems using the restricted-user detached-tree path.
Affected software
Util-linux
How to mitigate CVE-2026-78409
Install security update from vendor's website.
Util-linux - addressed in versions 2.41.6, 2.42.3