CVE-2026-90038 NFSD: Prevent client use-after-free during export state revocation
A use-after-free in the Linux kernel NFSD module allows attackers to cause denial of service or execute code during export state revocation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90038?
CVE-2026-90038 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 export state revocation
nfsd4_revoke_export_states() has the same use-after-free as nfsd4_revoke_states(): it drops nn->client_lock across revoke_one_stid() and the following read of clp->cl_minorversion, but the stateid reference it holds does not pin the client. A teardown racing the dropped lock can free the client while revoke_one_stid() still dereferences it.
exportfs -u drives this path through NFSD_CMD_UNLOCK_EXPORT, so an administrator removing an export can race a client expiry.
Skip a client that is already expiring and otherwise pin it with cl_rpc_users under client_lock before dropping the lock, matching nfsd4_revoke_states().
Which versions are affected by CVE-2026-90038?
How do I fix CVE-2026-90038?
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-2026-90038 being exploited?
There is no known exploitation of CVE-2026-90038 in the wild and no public exploit code.
Sources
Also known as GHSA-j297-c8rv-68vc, UBUNTU-CVE-2026-90038.