CVE-2026-89664 (GCVE-0-2026-89664)
Vulnerability from cvelistv5
Published
2026-09-11 19:45
Modified
2026-10-19 08:50
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: release OPEN-decoded posix ACLs via op_release nfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates refcounted struct posix_acl objects via posix_acl_alloc() and stores them in open->op_pacl and open->op_dpacl. These pointers must be released once the OPEN compound finishes. When nfsd4_decode_open_claim4() returns a non-seqid-mutating error, the dispatcher short-circuits before op_func runs: nfsd4_proc_compound() if (op->status && op->opnum == OP_OPEN) op->status = nfsd4_open_omfg(...) if (!seqid_mutating_err(ntohl(op->status))) return op->status; /* nfsd4_open() never runs */ ... opdesc->op_release(&op->u) /* must still release op_pacl/op_dpacl */ Before this change OP_OPEN had no .op_release in nfsd4_ops[], and the release pair lived inside nfsd4_open() at its out_err: label. On the short-circuit path nfsd4_open() is never invoked, so both posix_acl refs leak on every malformed OPEN compound that carries valid POSIX ACL createhow4 attributes. Add nfsd4_open_release() and wire it as .op_release for OP_OPEN. posix_acl_release() is NULL-safe, so the single release site covers both the normal path and the nfsd4_open_omfg short-circuit. Remove the matching posix_acl_release() pair from nfsd4_open()'s out_err: label to avoid double-releasing. The compound loop has two encoding branches: nfsd4_encode_operation() for normal ops, and nfsd4_encode_replay() for v4.0 replayed ops. op_release was only called from nfsd4_encode_operation(), so resources attached to op->u leak on the replay path. Move the op_release() call out of nfsd4_encode_operation() and the replay branch, placing it after the if-else in nfsd4_proc_compound(). This gives a single call site in a fairly obviously-correct place, covering both the normal encoding and replay paths.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05
Version: 5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c",
            "fs/nfsd/nfs4xdr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5b3a7d7c23c071efe12dd1bc1d2e5f97c4892921",
              "status": "affected",
              "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05",
              "versionType": "git"
            },
            {
              "lessThan": "8215892993ea9f5231da4fa9eb42428a286fce8b",
              "status": "affected",
              "version": "5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c",
            "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"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: release OPEN-decoded posix ACLs via op_release\n\nnfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates\nrefcounted struct posix_acl objects via posix_acl_alloc() and stores\nthem in open-\u003eop_pacl and open-\u003eop_dpacl. These pointers must be\nreleased once the OPEN compound finishes.\n\nWhen nfsd4_decode_open_claim4() returns a non-seqid-mutating error,\nthe dispatcher short-circuits before op_func runs:\n\n    nfsd4_proc_compound()\n      if (op-\u003estatus \u0026\u0026 op-\u003eopnum == OP_OPEN)\n          op-\u003estatus = nfsd4_open_omfg(...)\n              if (!seqid_mutating_err(ntohl(op-\u003estatus)))\n                  return op-\u003estatus;   /* nfsd4_open() never runs */\n      ...\n      opdesc-\u003eop_release(\u0026op-\u003eu)  /* must still release op_pacl/op_dpacl */\n\nBefore this change OP_OPEN had no .op_release in nfsd4_ops[], and the\nrelease pair lived inside nfsd4_open() at its out_err: label. On the\nshort-circuit path nfsd4_open() is never invoked, so both posix_acl\nrefs leak on every malformed OPEN compound that carries valid POSIX\nACL createhow4 attributes.\n\nAdd nfsd4_open_release() and wire it as .op_release for OP_OPEN.\nposix_acl_release() is NULL-safe, so the single release site covers\nboth the normal path and the nfsd4_open_omfg short-circuit. Remove\nthe matching posix_acl_release() pair from nfsd4_open()\u0027s out_err:\nlabel to avoid double-releasing.\n\nThe compound loop has two encoding branches: nfsd4_encode_operation()\nfor normal ops, and nfsd4_encode_replay() for v4.0 replayed ops.\nop_release was only called from nfsd4_encode_operation(), so resources\nattached to op-\u003eu leak on the replay path.\n\nMove the op_release() call out of nfsd4_encode_operation() and the\nreplay branch, placing it after the if-else in nfsd4_proc_compound().\nThis gives a single call site in a fairly obviously-correct place,\ncovering both the normal encoding and replay paths."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The leak is in nfsd NFSv4 OPEN XDR decoding (nfsd4_decode_createhow4 \u2192 nfsd4_decode_fattr4 \u2192 posix_acl_alloc), reached over the network via COMPOUND RPCs on TCP/UDP port 2049 when the in-kernel NFS server is running.\nAC:L - An attacker can deterministically leak the ACLs by sending OPEN with CREATE and valid POSIX ACL attributes, then a non-seqid-mutating decode error such as NFS4ERR_BADXDR on open_claim4, so nfsd4_open() never runs; no race or luck is required.\nPR:N - OPEN decode allocates the posix_acl objects after spoofable RPC AUTH_UNIX and before nfsd4_open(), fh_verify(), export permission checks, or clientid/session validation, so no authenticated NFS identity or local account on the server is required.\nUI:N - The attacker triggers the leak solely by sending crafted NFSv4 COMPOUND packets; no victim user must mount a filesystem, open a file, or take any other action.\nS:U - Impact is confined to kernel slab consumption on the NFS server host and does not cross a VM, guest, sandbox, or IOMMU security boundary.\nC:N - This is a refcount leak of attacker-supplied posix_acl allocations with no out-of-bounds read, use-after-free, or other primitive that could disclose kernel or file data.\nI:N - The short-circuit path never runs nfsd4_open() or writes file/ACL metadata; the only effect is orphaned kmalloc objects, with no memory corruption or unauthorized modification.\nA:H - Each malformed OPEN permanently leaks up to two posix_acl objects (NFS_ACL_MAX_ENTRIES=1024, about 16KB each) for the server lifetime; repeating the request exhausts kernel memory and can OOM the NFS server and co-hosted workloads."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:50:35.770Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5b3a7d7c23c071efe12dd1bc1d2e5f97c4892921"
        },
        {
          "url": "https://git.kernel.org/stable/c/8215892993ea9f5231da4fa9eb42428a286fce8b"
        }
      ],
      "title": "nfsd: release OPEN-decoded posix ACLs via op_release",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89664",
    "datePublished": "2026-09-11T19:45:51.319Z",
    "dateReserved": "2026-09-11T19:38:34.745Z",
    "dateUpdated": "2026-10-19T08:50:35.770Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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