Util-linux: util-linux: restricted bind mounts do not pin the source, allowing x-mount.owner/group/mode redirection
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in v2.41.6, v2.42.3
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: no
- Technical impact: total
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: poc · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- util-linux-main
Version range not reported
- util-linux
Version range not reported
- util-linux
Version range not reported
- util-linux
Version range not reported
- rhel8/flatpak-runtime
Version range not reported
- rhel8/flatpak-sdk
Version range not reported
- util-linux
Version range not reported
- openshift/ose-rhel-coreos-8
Version range not reported
- openshift/ose-rhel-coreos-9
Version range not reported
- openshift/ose-rhel-coreos-9
Version range not reported
References 4
access.redhat.com
bugzilla.redhat.com
GitHub · util-linux/util-linux
Questions about CVE-2026-78410
What does this mean?
A local unprivileged user can make a root-run SUID mount(8) redirect a bind mount to a directory of the attacker's choice, so root ends up changing the owner or mode of that host directory. The flaw is that restricted bind mounts do not pin their source.Source: access.redhat.com
Am I affected, and how do I check?
Affected versions are util-linux v2.39 through v2.42.2; earlier releases are not affected, since X-mount.owner, X-mount.group and X-mount.mode were introduced in v2.39. The issue needs an fstab entry that is a bind or rbind mount authorized for unprivileged users and also sets X-mount.owner, X-mount.group or X-mount.mode, and a source that a local user can replace with a symlink. Check your util-linux version with mount --version and review /etc/fstab for such entries.Source: access.redhat.com
What should I do about it?
Upgrade util-linux to v2.41.6 or v2.42.3, which contain the fix. Until then, avoid unprivileged /etc/fstab bind or rbind entries that also set X-mount.owner, X-mount.group or X-mount.mode, especially where the bind source is below a user-writable directory.Source: access.redhat.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data