Description
By default, jailed processes cannot mount filesystems, including nullfs(4). However, the allow.mount.nullfs option enables mounting nullfs filesystems, subject to privilege checks. If a privileged user within a jail is able to nullfs-mount directories, a limitation of the kernel's path lookup logic allows that user to escape the jail's chroot, yielding access to the full filesystem of the host or parent jail. In a jail configured to allow nullfs(4) mounts from within the jail, the jailed root user can escape the jail's filesystem root.
Problem types
CWE-269 Improper Privilege Management
Product status
14.3-RELEASE (release) before p8
13.5-RELEASE (release) before p9
References
security.freebsd.org/advisories/FreeBSD-SA-26:02.jail.asc