{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89686", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.749Z", "datePublished": "2026-09-11T19:46:07.877Z", "dateUpdated": "2026-10-21T12:48:21.196Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:48:21.196Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke\n\nnfsd4_alloc_layout_stateid reads fp->fi_deleg_file without holding\nfi_lock when the parent stateid is a delegation. A concurrent delegation\nrevoke via the laundromat can clear fi_deleg_file under fi_lock, causing\nnfsd_file_get() to return NULL and triggering the BUG_ON.\n\nThis race is client-reachable: two NFS clients can trigger it by having\none hold a delegation while another opens the same file to force a\nrecall. When the first client doesn't respond to the recall, the\nlaundromat revokes it. A concurrent LAYOUTGET from any client using the\ndelegation stateid hits the race window.\n\nFix this by taking fi_lock around the fi_deleg_file read in the\nSC_TYPE_DELEG path, matching the locking discipline of the\nfind_any_file() arm, and replacing the BUG_ON with a graceful error\nreturn that cleans up the partially-initialized layout stateid." } ], "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 flaw is in nfsd pNFS LAYOUTGET (nfsd4_alloc_layout_stateid in fs/nfsd/nfs4layouts.c). A remote NFSv4.1 client reaches it over TCP/2049 via nfsd_dispatch to nfsd4_proc_compound to nfsd4_layoutget, so no local access to the NFS server is required.\nAC:L - The attacker controls both sides of the race: one NFS client obtains a delegation while another OPENs the same file to force recall, then the first client withholds CB_RECALL and issues concurrent LAYOUTGET with the delegation stateid as the laundromat runs put_deleg_file. The sequence is retryable and can be timed using FATTR4_LEASE_TIME.\nPR:N - Typical nfsd deployments accept AUTH_SYS/AUTH_NULL without cryptographic authentication. Any host allowed by the export ACL can EXCHANGE_ID/CREATE_SESSION, OPEN to receive a delegation, and LAYOUTGET; no local account or capability on the NFS server is required.\nUI:N - The attacking NFS clients drive the OPEN, recall, and LAYOUTGET compounds themselves against an already-running nfsd export. No victim user action such as mounting a filesystem or opening a file on the server is required.\nS:U - The unlocked fi_deleg_file load and resulting BUG_ON or nfsd_file use-after-free occur in kernel nfsd state on the NFS server host. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - put_deleg_file may drop the last nfsd_file ref and call_rcu-free it (KMEM_CACHE flags 0, not SLAB_TYPESAFE_BY_RCU) while LAYOUTGET still calls nfsd_file_get on the stale pointer. After slab reuse the layout stateid's nf_file can be leveraged for kernel information disclosure.\nI:H - The same stale nfsd_file pointer is used for refcount_inc_not_zero and later nfsd4_layout_setlease/kernel_setlease on nf_file. Heap reuse of the nfsd_file slab enables an arbitrary write or control-flow hijack per kernel UAF scoring guidance.\nA:H - When nfsd_file_get returns NULL the original code hits BUG_ON(!ls->ls_file), oopsing or panicking the nfsd thread. Even without that assertion, use-after-free of nfsd_file crashes nfsd, and the attacker can repeat LAYOUTGET to deny NFS service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfs4layouts.c" ], "versions": [ { "version": "c5c707f96fc9a6e5a57ca5baac892673270abe3d", "lessThan": "d12af460df27876661707efab3a8532146cb961f", "status": "affected", "versionType": "git" }, { "version": "c5c707f96fc9a6e5a57ca5baac892673270abe3d", "lessThan": "c517f27498757e616d2a8fe6d16caad1fee422e6", "status": "affected", "versionType": "git" }, { "version": "c5c707f96fc9a6e5a57ca5baac892673270abe3d", "lessThan": "607a56fea772c1f4f4989d8e255dd4f7192d9604", "status": "affected", "versionType": "git" }, { "version": "c5c707f96fc9a6e5a57ca5baac892673270abe3d", "lessThan": "97bda8b4284d90897a1f1922e5082ff9e35d7c7e", "status": "affected", "versionType": "git" }, { "version": "c5c707f96fc9a6e5a57ca5baac892673270abe3d", "lessThan": "ca94ba36172046be6a694a7986f6931e47ed4d51", "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/nfs4layouts.c" ], "versions": [ { "version": "4.0", "status": "affected" }, { "version": "0", "lessThan": "4.0", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "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": "4.0", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/d12af460df27876661707efab3a8532146cb961f" }, { "url": "https://git.kernel.org/stable/c/c517f27498757e616d2a8fe6d16caad1fee422e6" }, { "url": "https://git.kernel.org/stable/c/607a56fea772c1f4f4989d8e255dd4f7192d9604" }, { "url": "https://git.kernel.org/stable/c/97bda8b4284d90897a1f1922e5082ff9e35d7c7e" }, { "url": "https://git.kernel.org/stable/c/ca94ba36172046be6a694a7986f6931e47ed4d51" } ], "title": "nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89686", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:26:03.140311Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:48.827Z" } } ] } }