CVE-2025-15547: Jail escape by a privileged user via nullfs
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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-15547?
The severity of CVE-2025-15547 is considered high due to the potential for a privileged user to escape a jail environment.
How do I fix CVE-2025-15547?
To fix CVE-2025-15547, it is recommended to disable the allow.mount.nullfs option in your FreeBSD jails.
What versions of FreeBSD are affected by CVE-2025-15547?
CVE-2025-15547 affects FreeBSD versions 13.5 and 14.3 across multiple patch levels.
Can a non-privileged user exploit CVE-2025-15547?
No, only a privileged user within a jail can exploit CVE-2025-15547 by mounting nullfs directories.
What is nullfs and its role in CVE-2025-15547?
Nullfs is a filesystem type in FreeBSD that allows mounting directories within a jail, which can be misused if the allow.mount.nullfs option is enabled.