CVE-2026-78410

Summary

A flaw was found in util-linux. Restricted bind mounts take the source path from fstab but do not pin that source before the privileged mount. A local unprivileged user who can replace the authorized source or a writable ancestor can redirect SUID mount(8) to bind another host directory. If the fstab entry also sets X-mount.owner, X-mount.group, or X-mount.mode, root then changes ownership or mode on that redirected inode.

Affected Software

Weaknesses

• CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

Workarounds

Upgrade to util-linux v2.41.6, v2.42.3, or later. Until a fix is applied, do not allow unprivileged /etc/fstab bind or rbind entries that also specify X-mount.owner, X-mount.group, or X-mount.mode, especially when the bind source is below a user-writable ancestor.

References

• https://access.redhat.com/security/cve/CVE-2026-78410
• https://bugzilla.redhat.com/show_bug.cgi?id=2522684
• https://github.com/util-linux/util-linux/security/advisories/GHSA-rh77-686x-2f2m

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