CVE-2026-89668 nfsd: move nfsd_debugfs_init() after nfsd4_init_slabs() in init_nfsd()
A use-after-free vulnerability in the Linux kernel NFS server allows attackers to execute arbitrary code or cause a denial of service via stale debugfs pointers.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89668?
CVE-2026-89668 is a high-severity use after free vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
nfsd: move nfsd_debugfs_init() after nfsd4_init_slabs() in init_nfsd()
nfsd_debugfs_init() runs before nfsd4_init_slabs() in init_nfsd(). If the slab allocation fails, the bare "return retval" bypasses nfsd_debugfs_exit(), leaving orphan debugfs files with stale fops pointers into the freed module text.
Move nfsd_debugfs_init() to after the slab init succeeds, so the early return has no debugfs state to clean up.
Since debugfs is now the more recently initialized of the two, also update the unwind paths to match reverse-initialization (LIFO) order: run nfsd_debugfs_exit() before nfsd4_free_slabs() in both the init_nfsd() error path and exit_nfsd(). The nfsd debugfs files only reference module-global state and have no dependency on the slab caches, so that reordering is a cleanup with no functional change.
Which versions are affected by CVE-2026-89668?
How do I fix CVE-2026-89668?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89668 being exploited?
There is no known exploitation of CVE-2026-89668 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89668, DEBIAN-CVE-2026-89668, GHSA-9vcc-j8g4-f8ff, UBUNTU-CVE-2026-89668.