CVE-2026-89695

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-89695", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.750Z", "datePublished": "2026-09-11T19:46:14.258Z", "dateUpdated": "2026-10-19T08:51:08.488Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:08.488Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: cap decoded POSIX ACL count to bound sort cost\n\nnfsd4_decode_posixacl() reads a u32 entry count off the wire and passes\nit straight to posix_acl_alloc() and sort_pacl_range(). The latter is\nan O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in\nthe server's compound processing path.\n\n nfsd4_decode_posixacl()\n xdr_stream_decode_u32(&count) /* uncapped u32 */\n posix_acl_alloc(count, GFP_KERNEL)\n sort_pacl_range(*acl, 0, count - 1) /* O(n^2) bubble sort */\n\nThe encoder side in the same file already rejects ACLs whose a_count\nexceeds NFS_ACL_MAX_ENTRIES, but the decoder introduced in commit\n5fc51dfc2eb1 (\"NFSD: Add support for XDR decoding POSIX draft ACLs\")\nomitted the symmetric check.\n\nFix by rejecting a wire count greater than NFS_ACL_MAX_ENTRIES with\nnfserr_inval, before any allocation, so the sort is bounded by\nNFS_ACL_MAX_ENTRIES^2 comparisons.\n\nWhile we're in here, also fix the nfserr_resource return if\nposix_acl_alloc() fails. That's not a legal error code for v4.1+. Change\nit to return nfserr_jukebox as that's more appropriate for memory\nallocation failures."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:N - The flaw is in nfsd's NFSv4 XDR decoder (nfsd4_decode_posixacl in fs/nfsd/nfs4xdr.c), reached when a remote client sends COMPOUND SETATTR, CREATE, or OPEN with POSIX draft ACL fattrs over TCP/2049.\nAC:L - The attacker supplies the u32 ACL count and reverse-sorted ACE payload on the wire; decode then runs sort_pacl_range() deterministically with no race, victim state, or memory-layout dependency.\nPR:N - nfsd4_decode_posixacl() runs during COMPOUND XDR decode before SEQUENCE, filehandle, export, or setattr checks; under AUTH_SYS, the common NFS flavor, RPC credentials are attacker-asserted and no secret is verified.\nUI:N - nfsd worker threads decode and sort the attacker's COMPOUND automatically; no local user or administrator action is required.\nS:U - Impact stays inside the host kernel's nfsd thread pool; this is not a VM escape, IOMMU bypass, or other cross-authority boundary.\nC:N - The bug only burns CPU while sorting a temporary decoded POSIX ACL; it does not read kernel or file contents, and a failed posix_acl_alloc() returns an NFS error without leaking memory.\nI:N - sort_pacl_range() only reorders the attacker's own temporary ACL buffer, which is discarded on error; no kernel memory is corrupted and no on-disk ACL is applied without later authorization.\nA:H - A client-chosen ACE count, practically hundreds of thousands within the 4MiB RPC payload, drives an un-preempted O(n^2) bubble sort in an nfsd thread, stalling the finite nfsd pool so repeated requests fully 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/nfs4xdr.c"], "versions": [{"version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "lessThan": "ea14d71d6ecb925673761bcf79f781f7dc9042cc", "status": "affected", "versionType": "git"}, {"version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "lessThan": "4bc1108e876153a2dd6d874052b99182c3603135", "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/nfs4xdr.c"], "versions": [{"version": "7.0", "status": "affected"}, {"version": "0", "lessThan": "7.0", "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": "7.0", "versionEndExcluding": "7.2.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/ea14d71d6ecb925673761bcf79f781f7dc9042cc"}, {"url": "https://git.kernel.org/stable/c/4bc1108e876153a2dd6d874052b99182c3603135"}], "title": "nfsd: cap decoded POSIX ACL count to bound sort cost", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/nfsd/nfs4xdr.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "ea14d71d6ecb925673761bcf79f781f7dc9042cc", "status": "affected", "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "versionType": "git"}, {"lessThan": "4bc1108e876153a2dd6d874052b99182c3603135", "status": "affected", "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/nfsd/nfs4xdr.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "7.0"}, {"lessThan": "7.0", "status": "unaffected", "version": "0", "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: cap decoded POSIX ACL count to bound sort cost\n\nnfsd4_decode_posixacl() reads a u32 entry count off the wire and passes\nit straight to posix_acl_alloc() and sort_pacl_range(). The latter is\nan O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in\nthe server's compound processing path.\n\n nfsd4_decode_posixacl()\n xdr_stream_decode_u32(&count) /* uncapped u32 */\n posix_acl_alloc(count, GFP_KERNEL)\n sort_pacl_range(*acl, 0, count - 1) /* O(n^2) bubble sort */\n\nThe encoder side in the same file already rejects ACLs whose a_count\nexceeds NFS_ACL_MAX_ENTRIES, but the decoder introduced in commit\n5fc51dfc2eb1 (\"NFSD: Add support for XDR decoding POSIX draft ACLs\")\nomitted the symmetric check.\n\nFix by rejecting a wire count greater than NFS_ACL_MAX_ENTRIES with\nnfserr_inval, before any allocation, so the sort is bounded by\nNFS_ACL_MAX_ENTRIES^2 comparisons.\n\nWhile we're in here, also fix the nfserr_resource return if\nposix_acl_alloc() fails. That's not a legal error code for v4.1+. Change\nit to return nfserr_jukebox as that's more appropriate for memory\nallocation failures."}], "id": "CVE-2026-89695", "lastModified": "2026-10-19T09:18:08.037", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-09-11T20:19:56.610", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/4bc1108e876153a2dd6d874052b99182c3603135"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ea14d71d6ecb925673761bcf79f781f7dc9042cc"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: Linux kernel nfsd: Denial of Service via uncapped POSIX ACL count", "id": "2532373", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2532373"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-606", "details": ["A flaw was found in the Linux kernel's Network File System Daemon (nfsd). The `nfsd4_decode_posixacl()` function, responsible for decoding POSIX Access Control Lists (ACLs), does not properly cap the entry count received from a client. A remote attacker can exploit this by sending a specially crafted ACL with an excessively large entry count, leading to unbounded CPU usage during an O(n^2) sorting operation. This can result in a Denial of Service (DoS) for the affected server."], "name": "CVE-2026-89695", "public_date": "2026-09-11T19:46:14Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-89695\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-89695\nhttps://git.kernel.org/stable/c/4bc1108e876153a2dd6d874052b99182c3603135\nhttps://git.kernel.org/stable/c/ea14d71d6ecb925673761bcf79f781f7dc9042cc"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05,ea14d71d6ecb925673761bcf79f781f7dc9042cc)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05,4bc1108e876153a2dd6d874052b99182c3603135)"}}], "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": "generic", "value": "7.0"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,7.0)"}}, {"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": "2026-09-12T09:15:12.756645+00:00", "updated": "2026-09-15T20:45:20.768745+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}