{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90036", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.782Z", "datePublished": "2026-09-16T10:33:35.967Z", "dateUpdated": "2026-10-21T12:49:32.115Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:49:32.115Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during blocked-lock reaping\n\nA bare lock owner -- its only remaining reference a blocked lock on\nnn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but\nno reference keeping the client alive. When the per-net laundromat\nreaps such a lock, freeing the nbl drops the owner reference\nheld through flc_owner, and the final nfs4_put_stateowner()\ntakes the client's cl_lock. Because the laundromat detaches the\nnbl first, __destroy_client() no longer finds it, so a concurrent\nforce_expire_client() can free the client before nfs4_put_stateowner()\nruns, dereferencing cl_lock in freed memory.\n\nPin the client with cl_rpc_users before dropping\nnn->blocked_locks_lock, and skip clients already expiring, whose\nblocked locks __destroy_client() frees while holding an owner\nreference. Take nn->client_lock outside nn->blocked_locks_lock.\nEvery other site holds nn->blocked_locks_lock as a leaf, acquiring\nno further lock, so placing nn->client_lock outside it cannot form\na lock-order cycle." } ], "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 - NFSD is the in-kernel NFS server; the UAF is reached by remote NFSv4.1 COMPOUND RPCs over TCP/UDP 2049 (EXCHANGE_ID, CREATE_SESSION, OPEN, blocking LOCK, DESTROY_SESSION, DESTROY_CLIENTID) that queue a blocked lock and expire the client while nfs4_laundromat() reaps it.\nAC:L - The attacker controls both sides: one client holds a conflicting lock while another queues a FILE_LOCK_DEFERRED blocked lock (bare lockowner), then DESTROY_CLIENTID races with laundromat free_blocked_lock() after nbl detach; concurrent compounds create the race and it is retryable.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL with no cryptographic RPC authentication. A remote peer that can reach an export can create NFSv4.1 state and issue DESTROY_CLIENTID (ALLOWED_WITHOUT_FH) 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 is of struct nfs4_client in the NFS server kernel and does not cross a separate security authority such as a VM, guest/host, sandbox, or IOMMU boundary.\nC:H - free_blocked_lock() drops flc_owner into nfs4_put_stateowner(), which takes cl_lock on a nfs4_client already freed by concurrent expire_client(). The mergeable client_slab object (KMEM_CACHE flags 0) can be reclaimed via EXCHANGE_ID to disclose kernel memory.\nI:H - nfs4_put_stateowner() does atomic_dec_and_lock on the freed client's cl_lock and so_unhash walks client-owned lists; reclaiming the nfs4_client slab enables heap corruption and control-flow hijack. Kernel guidance scores use-after-free as I:H.\nA:H - Use-after-free of nfs4_client (spin_lock of freed cl_lock) in the laundromat worker 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": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b", "lessThan": "0d53a47c913d0bce3b5ec35c28cbcca4d015f33d", "status": "affected", "versionType": "git" }, { "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b", "lessThan": "7081224a59a0ca4edcd62c068588f4d900199a18", "status": "affected", "versionType": "git" }, { "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b", "lessThan": "cd489b03587378645fe0d20142a33f1ed60bac98", "status": "affected", "versionType": "git" }, { "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b", "lessThan": "6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0", "status": "affected", "versionType": "git" }, { "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b", "lessThan": "9026932ac8be4d0ae01db47f23619a98cc57b671", "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": "4.9", "status": "affected" }, { "version": "0", "lessThan": "4.9", "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": "7.2.5", "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": "4.9", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9", "versionEndExcluding": "6.18.51" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9", "versionEndExcluding": "7.2.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/0d53a47c913d0bce3b5ec35c28cbcca4d015f33d" }, { "url": "https://git.kernel.org/stable/c/7081224a59a0ca4edcd62c068588f4d900199a18" }, { "url": "https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98" }, { "url": "https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0" }, { "url": "https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671" } ], "title": "NFSD: Prevent client use-after-free during blocked-lock reaping", "x_generator": { "engine": "bippy-1.2.0" } } } }