{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90038","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.782Z","datePublished":"2026-09-16T10:33:37.366Z","dateUpdated":"2026-09-16T14:41:51.107Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-16T14:41:51.107Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during export state revocation\n\nnfsd4_revoke_export_states() has the same use-after-free as\nnfsd4_revoke_states(): it drops nn->client_lock across\nrevoke_one_stid() and the following read of clp->cl_minorversion, but\nthe stateid reference it holds does not pin the client.  A teardown\nracing the dropped lock can free the client while revoke_one_stid()\nstill dereferences it.\n\nexportfs -u drives this path through NFSD_CMD_UNLOCK_EXPORT, so an\nadministrator removing an export can race a client expiry.\n\nSkip a client that is already expiring and otherwise pin it with\ncl_rpc_users under client_lock before dropping the lock, matching\nnfsd4_revoke_states()."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The UAF is in nfsd nfsd4_revoke_export_states(). A remote NFSv4 peer reaches the racing expire_client() over TCP/2049 via svc_recv to nfsd_dispatch to nfsd4_proc_compound: EXCHANGE_ID/CREATE_SESSION, SETCLIENTID_CONFIRM, or DESTROY_CLIENTID (ALLOWED_WITHOUT_FH), which free nfs4_client while the export-revoke walk still dereferences it.\nAC:L - The attacker controls the teardown side: they hold many stateids on the export so the revoke walk drops client_lock once per stid, and concurrently retry EXCHANGE_ID/CREATE_SESSION or SETCLIENTID_CONFIRM so mark_client_expired_locked() succeeds while cl_rpc_users is unpinned. The window is retryable and attacker-created.\nPR:N - EXCHANGE_ID, CREATE_SESSION, SETCLIENTID, SETCLIENTID_CONFIRM, and DESTROY_CLIENTID are ALLOWED_WITHOUT_FH with no export check. Typical AUTH_SYS/AUTH_NULL nfsd deployments do not verify RPC credentials, so any host that can reach TCP/2049 can establish state on an export and trigger expire.\nUI:N - The attacker drives the NFS compounds that create state and expire the client. Administrative exportfs -u / NFSD_CMD_UNLOCK_EXPORT is a server operational condition (unexport of the last client for a path so the filesystem can be unmounted), not a required victim user action.\nS:U - The freed object is struct nfs4_client in the NFS server kernel. Impact remains in that kernel security authority; there is no VM, IOMMU, or sandbox boundary crossing.\nC:H - revoke_one_stid() and the subsequent clp->cl_minorversion read dereference nfs4_client after free_client() kmem_cache_free's the mergeable client_slab object (KMEM_CACHE flags 0). Reclaim via EXCHANGE_ID discloses kernel memory; a UAF is C:H.\nI:H - revoke_one_stid() takes cl_lock and nfs4_put_stid() does refcount_dec_and_lock/idr_remove on the freed client's cl_lock/cl_stateids, concurrent with __destroy_client(), a slab UAF write primitive for heap corruption and control-flow hijacking.\nA:H - Use-after-free of nfs4_client in the nfsd export-revoke path oopses or panics the NFS server even without full exploitation, fully denying service of the host."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"],"versions":[{"version":"2eac189bb059d31a29937b29ee0f477394198610","lessThan":"c05ae58fe06ce2ac34312f649e71c3596bdde358","status":"affected","versionType":"git"},{"version":"2eac189bb059d31a29937b29ee0f477394198610","lessThan":"2108de53568a64936a0da3e04d85c35df98d3fb6","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"],"versions":[{"version":"7.2","status":"affected"},{"version":"0","lessThan":"7.2","status":"unaffected","versionType":"semver"},{"version":"7.2.5","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.2.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/c05ae58fe06ce2ac34312f649e71c3596bdde358"},{"url":"https://git.kernel.org/stable/c/2108de53568a64936a0da3e04d85c35df98d3fb6"}],"title":"NFSD: Prevent client use-after-free during export state revocation","x_generator":{"engine":"bippy-1.2.0"}}}}