{
    "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"
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}