CVE-2026-98995 namespace: reset the old parent's ->overmount in mnt_change_mountpoint()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-98995?
CVE-2026-98995 is a high-severity vulnerability in Linux, published on 23 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
namespace: reset the old parent's ->overmount in mnt_change_mountpoint()
__umount_mnt() resets ->overmount of the parent when it unmounts the mount that overmounts it. mnt_change_mountpoint() doesn't. It moves the mount to its new parent and leaves the old one pointing at it.
For a mount that is moved beneath in attach_recursive_mnt() that doesn't matter. The new mount has already reset ->overmount of the old parent by the time the old top mount is moved onto it.
It matters for reparent() though. propagate_umount() moves a surviving overmount onto the first ancestor that isn't going to be unmounted. The mount it was taken from is unmounted immediately afterwards. If a file descriptor keeps that unmounted mount alive ->overmount points at the moved mount. That's a dangling pointer and UAF as the moved mount is unmounted and freed.
do_lock_mount() follows ->overmount from the target path under mount_lock. With a file descriptor on such a mount as the target of a mount beneath topmost_overmount() walks into the freed mount and do_lock_mount() takes references on whatever it finds there.
So reset ->overmount of the old parent in mnt_change_mountpoint() the same way __umount_mnt() does. A mount's ->overmount is then always a mount that is attached to it.
Which versions are affected by CVE-2026-98995?
How do I fix CVE-2026-98995?
Upgrade to a fixed version.
Is CVE-2026-98995 being exploited?
There is no known exploitation of CVE-2026-98995 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98995, DEBIAN-CVE-2026-98995, GHSA-h4q9-qcg7-rj48, UBUNTU-CVE-2026-98995.