CVE-2026-78409
highThe X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW.
The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with an fstab-authorized X-mount.subdir entry can attach a host path at the intended mountpoint.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://access.redhat.com/errata/RHSA-2026:63162 secalert@redhat.com
- https://access.redhat.com/security/cve/CVE-2026-78409 secalert@redhat.com
- https://bugzilla.redhat.com/show_bug.cgi?id=2522607 secalert@redhat.com
- https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv secalert@redhat.com
- https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv 134c704f-9b21-4f2e-91b3-4a467353bcc0