{"id":"CVE-2026-89662","state":"PUBLISHED","title":"NFSD: Prevent lock owner use-after-free during client teardown","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent lock owner use-after-free during client teardown\n\n__destroy_client() releases a client's open owners, but a lock owner\nwhose only reference is a blocked lock (nbl) stays on\ncl_ownerstr_hashtbl.  client_has_state() does not count a bare owner,\nso DESTROY_CLIENTID can reach __destroy_client() with such owners\npresent.\n\n__destroy_client() then walks the table, calling remove_blocked_locks()\non each owner without a reference.  Freeing a blocked lock drops the\nowner reference held via flc_owner.  The per-net laundromat reaps\nblocked locks from nn->blocked_locks_lru independently of client state.\nThe two paths share blocked_locks_lock only for the list splice, not\nthe owner's lifetime.  The laundromat therefore frees the owner as\n__destroy_client() dereferences it, a NULL dereference in\nremove_blocked_locks().\n\nnfsd4_release_lockowner() holds a reference across the same call;\n__destroy_client() does not.  Hold cl_lock across the walk, taking a\nreference and unhashing each owner, then drop it before\nremove_blocked_locks() and nfs4_put_stateowner(), which take\nblocked_locks_lock and cl_lock.","publishedAt":"2026-09-11T19:45:49.833Z","updatedAt":"2026-10-19T08:50:33.792Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"42d7954b0a1907d4ef122aef94561952a033cdc3","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"b8bad5a11416b26cc7fd4b18fba46d75ff636558","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"1ce74d1b7770e69735e8f8e509807af4ff9c8ee7","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"a6ead6fff3a7d03e49845f048f7000a2e0d34431","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"4804c58f73a80d12df1de323bf97a164f6ee8743","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"8cf4ff0a7c083dd5e0067f517d63979b74b66649","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"5e2fa29d223a9a1e6a948e40b109d09081d1decd","versionType":"git"},{"version":"e294c4c2d33b7307a89cdf31bec08a112d6a9297","status":"affected","versionType":"git"},{"version":"797bfd05d4040fbf766198b3cfcc1838002cc890","status":"affected","versionType":"git"},{"version":"0f44e9da465ea259b6c9f31a627f3c50a16e1679","status":"affected","versionType":"git"},{"version":"4.9.91","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.14.31","status":"affected","lessThan":"4.15","versionType":"semver"},{"version":"4.15.14","status":"affected","lessThan":"4.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]}],"references":["https://git.kernel.org/stable/c/42d7954b0a1907d4ef122aef94561952a033cdc3","https://git.kernel.org/stable/c/bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a","https://git.kernel.org/stable/c/b8bad5a11416b26cc7fd4b18fba46d75ff636558","https://git.kernel.org/stable/c/1ce74d1b7770e69735e8f8e509807af4ff9c8ee7","https://git.kernel.org/stable/c/a6ead6fff3a7d03e49845f048f7000a2e0d34431","https://git.kernel.org/stable/c/4804c58f73a80d12df1de323bf97a164f6ee8743","https://git.kernel.org/stable/c/8cf4ff0a7c083dd5e0067f517d63979b74b66649","https://git.kernel.org/stable/c/5e2fa29d223a9a1e6a948e40b109d09081d1decd"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89662.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89662","state":"PUBLISHED","datePublished":"2026-09-11T19:45:49.833Z","dateUpdated":"2026-10-19T08:50:33.792Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.744Z"},"containers":{"cna":{"title":"NFSD: Prevent lock owner use-after-free during client teardown","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent lock owner use-after-free during client teardown\n\n__destroy_client() releases a client's open owners, but a lock owner\nwhose only reference is a blocked lock (nbl) stays on\ncl_ownerstr_hashtbl.  client_has_state() does not count a bare owner,\nso DESTROY_CLIENTID can reach __destroy_client() with such owners\npresent.\n\n__destroy_client() then walks the table, calling remove_blocked_locks()\non each owner without a reference.  Freeing a blocked lock drops the\nowner reference held via flc_owner.  The per-net laundromat reaps\nblocked locks from nn->blocked_locks_lru independently of client state.\nThe two paths share blocked_locks_lock only for the list splice, not\nthe owner's lifetime.  The laundromat therefore frees the owner as\n__destroy_client() dereferences it, a NULL dereference in\nremove_blocked_locks().\n\nnfsd4_release_lockowner() holds a reference across the same call;\n__destroy_client() does not.  Hold cl_lock across the walk, taking a\nreference and unhashing each owner, then drop it before\nremove_blocked_locks() and nfs4_put_stateowner(), which take\nblocked_locks_lock and cl_lock."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"42d7954b0a1907d4ef122aef94561952a033cdc3","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"b8bad5a11416b26cc7fd4b18fba46d75ff636558","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"1ce74d1b7770e69735e8f8e509807af4ff9c8ee7","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"a6ead6fff3a7d03e49845f048f7000a2e0d34431","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"4804c58f73a80d12df1de323bf97a164f6ee8743","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"8cf4ff0a7c083dd5e0067f517d63979b74b66649","versionType":"git"},{"version":"68ef3bc3166468678d5e1fdd216628c35bd1186f","status":"affected","lessThan":"5e2fa29d223a9a1e6a948e40b109d09081d1decd","versionType":"git"},{"version":"e294c4c2d33b7307a89cdf31bec08a112d6a9297","status":"affected","versionType":"git"},{"version":"797bfd05d4040fbf766198b3cfcc1838002cc890","status":"affected","versionType":"git"},{"version":"0f44e9da465ea259b6c9f31a627f3c50a16e1679","status":"affected","versionType":"git"},{"version":"4.9.91","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.14.31","status":"affected","lessThan":"4.15","versionType":"semver"},{"version":"4.15.14","status":"affected","lessThan":"4.16","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/42d7954b0a1907d4ef122aef94561952a033cdc3"},{"url":"https://git.kernel.org/stable/c/bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a"},{"url":"https://git.kernel.org/stable/c/b8bad5a11416b26cc7fd4b18fba46d75ff636558"},{"url":"https://git.kernel.org/stable/c/1ce74d1b7770e69735e8f8e509807af4ff9c8ee7"},{"url":"https://git.kernel.org/stable/c/a6ead6fff3a7d03e49845f048f7000a2e0d34431"},{"url":"https://git.kernel.org/stable/c/4804c58f73a80d12df1de323bf97a164f6ee8743"},{"url":"https://git.kernel.org/stable/c/8cf4ff0a7c083dd5e0067f517d63979b74b66649"},{"url":"https://git.kernel.org/stable/c/5e2fa29d223a9a1e6a948e40b109d09081d1decd"}],"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 NFSv4.1 client teardown and blocked-lock handling, reached by remote COMPOUND RPCs on the in-kernel NFS server (TCP/UDP 2049). A network client drives EXCHANGE_ID, CREATE_SESSION, OPEN, blocking LOCK, DESTROY_SESSION, and DESTROY_CLIENTID into __destroy_client().\nAC:L - The attacker controls both sides of the race: one client holds a conflicting lock while another queues a blocked lock, then DESTROY_CLIENTID races with lock-grant/CB_NOTIFY_LOCK or the laundromat freeing that lockowner. Concurrent NFS requests create the race, and it can be retried.\nPR:N - Typical nfsd deployments use AUTH_SYS, which does not cryptographically authenticate the client. A remote peer that can reach an export can create NFSv4.1 state and issue DESTROY_CLIENTID without a local account or kernel capabilities on the server.\nUI:N - Exploitation requires only attacker-sent NFS RPCs against a running nfsd export. No victim user action such as mounting a filesystem or opening a local file on the server is required.\nS:U - The use-after-free occurs in kernel nfsd lock-owner state on the NFS server host and does not cross a separate security authority such as a VM, guest/host, or IOMMU boundary.\nC:H - This is a use-after-free of the nfs4_lockowner slab object. Reclaiming the freed owner lets an attacker control later reads of so_client and related pointers in remove_blocked_locks(), yielding a kernel information-disclosure primitive.\nI:H - The same UAF is exploitable for integrity: the freed lockowner includes so_ops function pointers and lo_blocked list heads, so heap reuse can hijack control flow or corrupt list pointers for an arbitrary kernel write.\nA:H - The bug is a kernel use-after-free of the lock owner and was observed as a NULL dereference in remove_blocked_locks(), which can oops or panic nfsd and take down the server."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:50:33.792Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"5.10.270"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9.91"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.31"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15.14"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-89662","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T19:25:37.406747Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:26:47.751Z"}}]}}}