A flaw was found in util-linux. (CVE-2026-78410)

The flaw in util-linux involves restricted bind mounts that take the source path from fstab without pinning that source before a privileged mount operation. An unprivileged local user who can replace the authorized source or a writable ancestor directory can redirect the SUID mount(8) command to bind a different host directory. If the fstab entry includes options such as X-mount.owner, X-mount.group, or X-mount.mode, root will then apply ownership or mode changes to the redirected inode, potentially escalating privileges or altering system state.

This vulnerability allows a local unprivileged user to redirect privileged mount operations to arbitrary directories, causing root to change ownership or permissions on those directories. This can lead to privilege escalation or unauthorized modification of filesystem metadata, impacting system integrity and security.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict local user permissions to prevent replacement of authorized source paths or writable ancestor directories used in fstab entries with restricted bind mounts.