util-linux: util-linux: X-mount.subdir detached-tree resolution can escape via intermediate symlinks

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

EUVD-2026-70107

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409 Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409 Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

CVE-2026-78409

A flaw in util-linux 's X-mount.subdir mount option allows a local unprivileged user to escape the intended subdirectory and attach an arbitrary host path at the intended mountpoint. On Linux 6.15 and later , the option takes a detached-tree fast path that calls open_tree() with AT_SYMLINK_NOFOLL...

CVE-2026-78409

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to opentree with ATSYMLINKNOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with...

PT-2026-84765

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...