{"id":"CVE-2026-78409","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-78409","summary":"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…","details":"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.","published":"2026-09-02T16:17:23.833","modified":"2026-09-02T16:17:23.833","cvss":{"score":7,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":null,"references":[{"type":"WEB","url":"https://access.redhat.com/security/cve/CVE-2026-78409"},{"type":"WEB","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2522607"},{"type":"WEB","url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv"},{"type":"WEB","url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-09-02T16:17:23.833"}}