CVE-2026-90037 NFSD: Prevent client use-after-free during close_lru reaping
A race condition in the Linux kernel NFSD allows attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90037?
CVE-2026-90037 is a critical use after free vulnerability in Linux, published on 16 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:
NFSD: Prevent client use-after-free during close_lru reaping
An nfs4_openowner left on nn->close_lru after its final CLOSE keeps its last closed stateid in oo_last_closed_stid, holding only a raw pointer to its nfs4_client. The laundromat reaps timed-out entries, drops nn->client_lock, and calls nfs4_put_stid(), which dereferences the client through cl_lock. Nothing pins the client across that window, so a concurrent force_expire_client() can free it and nfs4_put_stid() reads freed memory. __destroy_client() hits the same race, walking clp->cl_openowners without cl_lock.
Pin the client with cl_rpc_users before dropping client_lock, and skip clients already expiring. __destroy_client() then cleans up its own close_lru entries through release_last_closed_stateid(), so teardown no longer races the laundromat.
Which versions are affected by CVE-2026-90037?
How do I fix CVE-2026-90037?
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-2026-90037 being exploited?
There is no known exploitation of CVE-2026-90037 in the wild and no public exploit code.
Sources
Also known as AZL-101642, BELL-CVE-2026-90037, DEBIAN-CVE-2026-90037, GHSA-cj69-89jw-ggxp, UBUNTU-CVE-2026-90037.