CVE-2026-89670

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-89670", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.746Z", "datePublished": "2026-09-11T19:45:55.846Z", "dateUpdated": "2026-10-19T08:50:43.628Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:43.628Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n CPU 0 (nfsd_open_local_fh) CPU 1 (nfsd_file_put_local)\n ----- -----\n new = cmpxchg(pnf, NULL, ...)\n nf = xchg(pnf, NULL)\n nfsd_file_put(nf)\n last ref -> call_rcu()\n /* grace period elapses;\n slab page recycled */\n nfsd_file_get(new)\n refcount_inc_not_zero(&new->nf_ref)\n /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - nfsd_open_local_fh is invoked only from the NFS client's LOCALIO path (nfs_generic_pg_pgios/nfs_commit_list \u2192 nfs_local_open_fh) after a same-host UUID handshake; a remote NFS peer never reaches this cmpxchg retry, so exploitation requires local access to a loopback NFS mount.\nAC:L - The attacker controls both sides of the race: concurrent read/write/commit syscalls enter nfsd_open_local_fh while close/put_nfs_open_context runs nfsd_file_put_local on the same nfs_file_localio slot; the sequence is repeatable at will and can be widened by preemption.\nPR:L - Any unprivileged local user who can open files on a LOCALIO-enabled NFS mount can reach nfs_generic_pg_pgios \u2192 nfsd_open_local_fh with no capability check; starting nfsd or creating the mount is a deployment precondition, not a privilege the attacker must hold.\nUI:N - The attacker triggers the use-after-free from their own threads via I/O and close syscalls; no separate victim action is required once the LOCALIO mount exists.\nS:U - The use-after-free corrupts nfsd_file slab objects in the host kernel, which is standard kernel memory corruption within one security authority, not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - nfsd_file is freed via call_rcu without SLAB_TYPESAFE_BY_RCU, so after the grace period nfsd_file_get and later nf_file/nf_net dereferences operate on recycled memory, enabling an arbitrary kernel read or disclosure of another exported file's contents.\nI:H - refcount_inc_not_zero writes into the recycled nfsd_file, and the stale pointer is then used for write_iter, corrupting another object's refcount and enabling a follow-on premature free and control-flow hijack.\nA:H - Use-after-free on the nfsd_file slab causes slab corruption, refcount warnings, and oops/panic when nf_file is taken from freed memory, which is a repeatable local kernel denial of service."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/localio.c"], "versions": [{"version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "lessThan": "763c0bad872368304db718f79af7e93048885c67", "status": "affected", "versionType": "git"}, {"version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "lessThan": "559570f91a7d4d199a72105e4980bef791f4cbf1", "status": "affected", "versionType": "git"}, {"version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "lessThan": "58884694978a3d7d111edb433d7fd6a6c5af2f34", "status": "affected", "versionType": "git"}, {"version": "986a21ace186433e0397a59491646edad8c8d636", "status": "affected", "versionType": "git"}, {"version": "6.15.3", "lessThan": "6.16", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/localio.c"], "versions": [{"version": "6.16", "status": "affected"}, {"version": "0", "lessThan": "6.16", "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": "6.16", "versionEndExcluding": "6.18.50"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.2.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67"}, {"url": "https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1"}, {"url": "https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34"}], "title": "nfsd: hold rcu across localio cmpxchg retry", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/nfsd/localio.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "763c0bad872368304db718f79af7e93048885c67", "status": "affected", "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "versionType": "git"}, {"lessThan": "559570f91a7d4d199a72105e4980bef791f4cbf1", "status": "affected", "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "versionType": "git"}, {"lessThan": "58884694978a3d7d111edb433d7fd6a6c5af2f34", "status": "affected", "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd", "versionType": "git"}, {"status": "affected", "version": "986a21ace186433e0397a59491646edad8c8d636", "versionType": "git"}, {"lessThan": "6.16", "status": "affected", "version": "6.15.3", "versionType": "semver"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/nfsd/localio.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.16"}, {"lessThan": "6.16", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.50", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.4", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n CPU 0 (nfsd_open_local_fh) CPU 1 (nfsd_file_put_local)\n ----- -----\n new = cmpxchg(pnf, NULL, ...)\n nf = xchg(pnf, NULL)\n nfsd_file_put(nf)\n last ref -> call_rcu()\n /* grace period elapses;\n slab page recycled */\n nfsd_file_get(new)\n refcount_inc_not_zero(&new->nf_ref)\n /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block."}], "id": "CVE-2026-89670", "lastModified": "2026-10-19T09:18:05.130", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-09-11T20:19:53.517", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: Linux kernel: nfsd use-after-free vulnerability due to missing RCU lock", "id": "2532286", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2532286"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-825", "details": ["A flaw was found in the Linux kernel's Network File System Daemon (nfsd) component. A race condition exists in the `nfsd_open_local_fh()` function where an `nfsd_file` object can be freed and its memory recycled while another process attempts to access it. This can lead to a use-after-free vulnerability, allowing an attacker to potentially cause memory corruption, disclose sensitive information, or execute arbitrary code."], "name": "CVE-2026-89670", "public_date": "2026-09-11T19:45:55Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-89670\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-89670\nhttps://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1\nhttps://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34\nhttps://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67"], "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e6f7e1487ab528a6c653bd0d42812ff2942846cd,763c0bad872368304db718f79af7e93048885c67)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e6f7e1487ab528a6c653bd0d42812ff2942846cd,559570f91a7d4d199a72105e4980bef791f4cbf1)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e6f7e1487ab528a6c653bd0d42812ff2942846cd,58884694978a3d7d111edb433d7fd6a6c5af2f34)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "986a21ace186433e0397a59491646edad8c8d636"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[6.15.3,6.16)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "6.16"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.16)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.50,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.4,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.3-rc1,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-09-12T06:15:04.246369+00:00", "updated": "2026-09-15T20:30:10.354073+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}