CVE-2026-89679 (GCVE-0-2026-89679)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
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: fix null dereference in nfsd4_setattr for deleg timestamp attrs When a SETATTR request includes FATTR4_WORD2_TIME_DELEG_ACCESS or FATTR4_WORD2_TIME_DELEG_MODIFY in the attribute bitmap, nfsd4_setattr() sets deleg_attrs=true and calls nfs4_preprocess_stateid_op() to validate the stateid. If the client supplies the NFSv4 "one stateid" (all-0xFF bytes), check_special_stateids() returns nfs_ok without populating the output nfs4_stid pointer, because the special-stateid path in nfs4_preprocess_stateid_op() jumps to done: with s==NULL, and the "if (s)" block that would set *cstid is skipped. The local variable `st` remains NULL. Back in nfsd4_setattr(), the if (deleg_attrs) block then unconditionally dereferences st->sc_type (at offset 4 from NULL), causing a kernel oops. This is remotely triggerable by any NFSv4 client: send COMPOUND [PUTROOTFH, SETATTR(ONE_STATEID, {bmval2=FATTR4_WORD2_TIME_DELEG_ACCESS, ...})]. No authentication, delegation, or prior state is required. Fix by adding a NULL check before the dereference. A special stateid is not a delegation stateid, so the existing nfserr_bad_stateid return value is already correct; we only need to guard the pointer dereference itself.
References
Impacted products
Vendor Product Version
Linux Linux Version: 7e13f4f8d27dc02fb88666f603c53ca749d56f92
Version: 7e13f4f8d27dc02fb88666f603c53ca749d56f92
Version: 7e13f4f8d27dc02fb88666f603c53ca749d56f92
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "3c5119b799a7f57db332b2c31e806de16c869f0f",
              "status": "affected",
              "version": "7e13f4f8d27dc02fb88666f603c53ca749d56f92",
              "versionType": "git"
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              "status": "affected",
              "version": "7e13f4f8d27dc02fb88666f603c53ca749d56f92",
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        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.14"
            },
            {
              "lessThan": "6.14",
              "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"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix null dereference in nfsd4_setattr for deleg timestamp attrs\n\nWhen a SETATTR request includes FATTR4_WORD2_TIME_DELEG_ACCESS or\nFATTR4_WORD2_TIME_DELEG_MODIFY in the attribute bitmap, nfsd4_setattr()\nsets deleg_attrs=true and calls nfs4_preprocess_stateid_op() to validate\nthe stateid.\n\nIf the client supplies the NFSv4 \"one stateid\" (all-0xFF bytes),\ncheck_special_stateids() returns nfs_ok without populating the output\nnfs4_stid pointer, because the special-stateid path in\nnfs4_preprocess_stateid_op() jumps to done: with s==NULL, and the\n\"if (s)\" block that would set *cstid is skipped. The local variable `st`\nremains NULL.\n\nBack in nfsd4_setattr(), the if (deleg_attrs) block then unconditionally\ndereferences st-\u003esc_type (at offset 4 from NULL), causing a kernel oops.\n\nThis is remotely triggerable by any NFSv4 client: send COMPOUND [PUTROOTFH,\nSETATTR(ONE_STATEID, {bmval2=FATTR4_WORD2_TIME_DELEG_ACCESS, ...})].\nNo authentication, delegation, or prior state is required.\n\nFix by adding a NULL check before the dereference. A special stateid is\nnot a delegation stateid, so the existing nfserr_bad_stateid return value\nis already correct; we only need to guard the pointer dereference itself."
        }
      ],
      "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 - nfsd is the in-kernel NFSv4 server; nfsd4_setattr() is reached from NFSPROC4_COMPOUND over TCP/2049. A remote peer triggers it with PUTROOTFH then SETATTR; no local access to the server is required.\nAC:L - COMPOUND [PUTROOTFH, SETATTR(ONE_STATEID, FATTR4_WORD2_TIME_DELEG_ACCESS)] makes check_special_stateids() return nfs_ok with st still NULL, then nfsd4_setattr() unconditionally reads st-\u003esc_type. The crash is deterministic; no race, special layout, or rare config is required.\nPR:N - The NULL deref runs in nfsd4_setattr() before nfsd_setattr()/nfsd_permission and needs no NFSv4 session, delegation, or prior state (v4.0 COMPOUND). Default AUTH_SYS/AUTH_NULL credentials are self-asserted, so any host that can reach the NFS port can trigger it.\nUI:N - The attacker sends the crafted NFSv4 COMPOUND themselves; no victim must mount an export, open a file, or otherwise interact.\nS:U - The NULL dereference oopses an nfsd thread on the NFS server. Impact stays inside that kernel\u0027s security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:N - This is a pure NULL-pointer read of st-\u003esc_type at offset 4 from NULL. It oopses without leaking kernel memory or providing an information-disclosure primitive.\nI:N - The bug only reads through a NULL nfs4_stid pointer; it does not write memory, corrupt adjacent objects, or yield a control-flow hijack. A remote NFS client cannot map the NULL page.\nA:H - The NULL dereference causes a kernel oops in the nfsd thread. Repeated requests can exhaust nfsd threads or panic the host (panic_on_oops), denying NFS service and taking down the server."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:50:52.556Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3c5119b799a7f57db332b2c31e806de16c869f0f"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c896db123892256fd39af0ee8c2d02c63539983"
        },
        {
          "url": "https://git.kernel.org/stable/c/fe456c8c0931bb3e8a03d429920e87fd85747fba"
        }
      ],
      "title": "nfsd: fix null dereference in nfsd4_setattr for deleg timestamp attrs",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89679",
    "datePublished": "2026-09-11T19:46:02.833Z",
    "dateReserved": "2026-09-11T19:38:34.747Z",
    "dateUpdated": "2026-10-19T08:50:52.556Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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