CVE-2026-90151 NFSv4: remove callback IDR entry on client allocation failure
A use-after-free vulnerability in the Linux kernel NFSv4 client allows attackers to trigger memory corruption and potentially execute code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90151?
CVE-2026-90151 is a critical use after free vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
NFSv4: remove callback IDR entry on client allocation failure
nfs4_alloc_client() allocates an NFSv4.0 callback identifier before it finishes setting up the client. If any later initialization step fails, the error path frees the nfs_client directly with nfs_free_client(). That bypasses nfs_put_client(), which is where the callback IDR entry is removed during normal teardown.
A failed allocation can therefore leave cb_ident_idr pointing at a freed nfs_client. A later NFSv4.0 callback lookup by cb_ident would find the stale pointer and take a reference to it.
Make the callback IDR removal helper callable by the allocation failure path, and remove the callback identifier before freeing the client.
This was found by a local static-analysis checker for publish-before-free lifetime bugs and confirmed by manual inspection.
Which versions are affected by CVE-2026-90151?
How do I fix CVE-2026-90151?
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-2026-90151 being exploited?
There is no known exploitation of CVE-2026-90151 in the wild and no public exploit code.
Sources
Also known as AZL-102821, BELL-CVE-2026-90151, DEBIAN-CVE-2026-90151, GHSA-h72c-5c39-xm46, UBUNTU-CVE-2026-90151.