High [CVE-2026-78410] Util-linux: util-linux: restricted bind mounts do not pin the source, allowing x-mount.owner/group/mode redirection
This high-severity Red Hat Linux advisory covers CVE-2026-78410 affecting Red Hat Enterprise Linux 10, Red Hat Hardened Images, Red Hat package: libblkid-devel.
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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.
X-mount.owner/group/mode was introduced in v2.39; earlier releases are not affected. Fixed in v2.41.6 and v2.42.3.
Red Hat severity: Important — CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-367.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Hardened Images. Red Hat lists Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4 as not affected.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: libblkid-devel; Red Hat package: libfdisk-devel; Red Hat package: libmount-devel; Red Hat package: libsmartcols-devel; and 5 more.
Affected products named by the advisory: Red Hat package: libuuid-devel; Red Hat package: python3-libmount; Red Hat package: util-linux-core; Red Hat package: util-linux.src; and 1 more.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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