{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89659", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.744Z", "datePublished": "2026-09-11T19:45:47.587Z", "dateUpdated": "2026-10-21T12:48:14.527Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:48:14.527Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during delegation revoke\n\nA delegation stateid holds only a bare pointer to its owning\nnfs4_client and does not keep it alive. The client survives its\nstateids only because __destroy_client() drains cl_delegations and\ncl_revoked before free_client() runs.\n\nnfs4_laundromat() breaks that invariant: it unhashes an\nexpired delegation from cl_delegations, drops deleg_lock, then\nrevoke_delegation() relinks it onto cl_revoked under cl_lock. In that\nwindow the delegation is on neither list, so client_has_state() can\nreport no remaining state.\n\nEvery teardown path first requires cl_rpc_users to be zero, but\nthe laundromat holds no such reference. A client whose recalled\ndelegation has just timed out can therefore reach free_client()\nwhile revoke_delegation() is still about to dereference cl_lock,\na use-after-free.\n\nPin the client with cl_rpc_users across the revoke so teardown blocks\nuntil it completes, then reap the delegation from cl_revoked. A client\nalready expiring reaps its own, so skip it and leave the delegation on\ndel_recall_lru." } ], "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 bug is in nfsd nfs4_laundromat()/revoke_delegation() in fs/nfsd/nfs4state.c. A remote NFSv4 client reaches it over TCP/2049 by OPEN to obtain a delegation, a conflicting OPEN to force CB_RECALL, then DESTROY_CLIENTID or CREATE_SESSION replacement while the laundromat revokes.\nAC:L - The attacker controls both sides: it creates the recalled delegation, learns FATTR4_LEASE_TIME, and issues DESTROY_CLIENTID or same-name CREATE_SESSION/SETCLIENTID_CONFIRM while laundromat unhashes. Many recalled delegations widen the unhash-to-revoke window, and the sequence is retryable.\nPR:N - Default AUTH_SYS nfsd exports do no cryptographic authentication; any host allowed by the export ACL can EXCHANGE_ID/SETCLIENTID, OPEN to get a delegation, and DESTROY_CLIENTID. No local account or capability on the NFS server is required.\nUI:N - The attacking NFS client performs the full sequence itself (delegation, recall, teardown). No local user or administrator action on the NFS server is required at attack time.\nS:U - The use-after-free corrupts the nfs4_client object in the host kernel's nfsd state tables. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - revoke_delegation() and nfs4_put_stid() dereference sc_client (cl_lock, cl_revoked, cl_stateids) after free_client() kmem_cache_free's the mergeable client_slab object (KMEM_CACHE flags 0), a UAF the attacker can reallocate via EXCHANGE_ID to disclose kernel memory.\nI:H - The UAF writes include spin_lock/unlock of freed cl_lock, list_add onto cl_revoked, and refcount_dec_and_lock in nfs4_put_stid on a reclaimable nfs4_client, enabling heap corruption and control-flow hijack.\nA:H - Use-after-free of nfs4_client in an nfsd/laundromat thread oopses or panics the NFS server even without full exploitation, and the attacker can repeat the RPC sequence to deny service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/netns.h", "fs/nfsd/nfs4state.c" ], "versions": [ { "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54", "lessThan": "94f0c73797c30a35812ffb32d11b8737d245c405", "status": "affected", "versionType": "git" }, { "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54", "lessThan": "0dd276b1324a5e08e83c6f675919946c9f0d61c9", "status": "affected", "versionType": "git" }, { "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54", "lessThan": "3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3", "status": "affected", "versionType": "git" }, { "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54", "lessThan": "2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56", "status": "affected", "versionType": "git" }, { "version": "3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54", "lessThan": "4683ca76b3b7e5808338491c6eb3c20e6b4894d5", "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/netns.h", "fs/nfsd/nfs4state.c" ], "versions": [ { "version": "3.10", "status": "affected" }, { "version": "0", "lessThan": "3.10", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.51", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "3.10", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.10", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.10", "versionEndExcluding": "6.18.51" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.10", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.10", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/94f0c73797c30a35812ffb32d11b8737d245c405" }, { "url": "https://git.kernel.org/stable/c/0dd276b1324a5e08e83c6f675919946c9f0d61c9" }, { "url": "https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3" }, { "url": "https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56" }, { "url": "https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5" } ], "title": "NFSD: Prevent client use-after-free during delegation revoke", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89659", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:25:33.821505Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:47.601Z" } } ] } }