{"id":"DEBIAN-CVE-2026-78409","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.","modified":"2026-09-16T22:00:06.822986787Z","published":"2026-09-02T16:17:23.833Z","upstream":["CVE-2026-78409"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-78409"}],"affected":[{"package":{"name":"util-linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/util-linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.38.1-5","2.38.1-5+deb12u1","2.38.1-5+deb12u2","2.38.1-5+deb12u3","2.38.1-5+loong64","2.38.1-6","2.39.1-1","2.39.1-2","2.39.1-3","2.39.1-4","2.39.2-1","2.39.2-2","2.39.2-2.1","2.39.2-2.2","2.39.2-3","2.39.2-4","2.39.2-5","2.39.2-6","2.39.3-1","2.39.3-10","2.39.3-11","2.39.3-2","2.39.3-3","2.39.3-4","2.39.3-5","2.39.3-6","2.39.3-6.1","2.39.3-6.1~exp1","2.39.3-7","2.39.3-8","2.39.3-9","2.40-1","2.40-2","2.40-3","2.40-4","2.40-5","2.40-6","2.40-7","2.40-8","2.40.1-1","2.40.1-2","2.40.1-3","2.40.1-4","2.40.1-4+hurd.1","2.40.1-6","2.40.1-7","2.40.1-8","2.40.1-8.1","2.40.1-9","2.40.2-1","2.40.2-10","2.40.2-11","2.40.2-12","2.40.2-12+hurd.1","2.40.2-13","2.40.2-14","2.40.2-2","2.40.2-3","2.40.2-4","2.40.2-5","2.40.2-6","2.40.2-7","2.40.2-8","2.40.2-9","2.40.3-1","2.40.4-1","2.40.4-2","2.40.4-3","2.40.4-4","2.40.4-5","2.40~rc2-1","2.40~rc2-2","2.40~rc2-3","2.40~rc2-4","2.40~rc2-5","2.40~rc2-6","2.40~rc2-7","2.40~rc2-8","2.41-1","2.41-2","2.41-3","2.41-4","2.41-5","2.41.1-1","2.41.1-2","2.41.1-3","2.41.1-4","2.41.2-1","2.41.2-2","2.41.2-3","2.41.2-4","2.41.3-1","2.41.3-2","2.41.3-3","2.41.3-4","2.41~rc1-1","2.41~rc1-2","2.41~rc2-1","2.42-1","2.42-2","2.42-3","2.42-4","2.42-5","2.42-6","2.42.1-1","2.42.1-2","2.42.1-3","2.42.1-4","2.42.1-5","2.42.1-6","2.42.2-1","2.42.2-2","2.42.2-3","2.42.2-4","2.42.3-1","2.42~rc1-1","2.42~rc1-2","2.42~rc1-3","2.42~rc2-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78409.json"}},{"package":{"name":"util-linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/util-linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.41-5","2.41.1-1","2.41.1-2","2.41.1-3","2.41.1-4","2.41.2-1","2.41.2-2","2.41.2-3","2.41.2-4","2.41.3-1","2.41.3-2","2.41.3-3","2.41.3-4","2.41.5-0+deb13u1","2.42-1","2.42-2","2.42-3","2.42-4","2.42-5","2.42-6","2.42.1-1","2.42.1-2","2.42.1-3","2.42.1-4","2.42.1-5","2.42.1-6","2.42.2-1","2.42.2-2","2.42.2-3","2.42.2-4","2.42.3-1","2.42~rc1-1","2.42~rc1-2","2.42~rc1-3","2.42~rc2-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78409.json"}},{"package":{"name":"util-linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/util-linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.42.3-1"}]}],"versions":["2.41-5","2.41.1-1","2.41.1-2","2.41.1-3","2.41.1-4","2.41.2-1","2.41.2-2","2.41.2-3","2.41.2-4","2.41.3-1","2.41.3-2","2.41.3-3","2.41.3-4","2.42-1","2.42-2","2.42-3","2.42-4","2.42-5","2.42-6","2.42.1-1","2.42.1-2","2.42.1-3","2.42.1-4","2.42.1-5","2.42.1-6","2.42.2-1","2.42.2-2","2.42.2-3","2.42.2-4","2.42~rc1-1","2.42~rc1-2","2.42~rc1-3","2.42~rc2-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78409.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}