Linux Kernel NFSD nfsd4_revoke_export_states use after free

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel. This affects the function nfsd4_revoke_export_states of the component NFSD. Executing a manipulation can lead to use after free. This vulnerability is handled as CVE-2026-90038. The attack can be executed remotely. There is not any exploit available. It is best practice to apply a patch to resolve this issue.

Detailsinfo

A vulnerability has been found in Linux Kernel (unknown version) and classified as very critical. This vulnerability affects the function nfsd4_revoke_export_states of the component NFSD. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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().

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-90038 since 09/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 09/16/2026).

Applying the patch c05ae58fe06ce2ac34312f649e71c3596bdde358/2108de53568a64936a0da3e04d85c35df98d3fb6 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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