CVE-2025-40326 (GCVE-0-2025-40326)
Vulnerability from cvelistv5
Published
2025-12-08 00:46
Modified
2026-08-05 12:09
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: Define actions for the new time_deleg FATTR4 attributes NFSv4 clients won't send legitimate GETATTR requests for these new attributes because they are intended to be used only with CB_GETATTR and SETATTR. But NFSD has to do something besides crashing if it ever sees a GETATTR request that queries these attributes. RFC 8881 Section 18.7.3 states: > The server MUST return a value for each attribute that the client > requests if the attribute is supported by the server for the > target file system. If the server does not support a particular > attribute on the target file system, then it MUST NOT return the > attribute value and MUST NOT set the attribute bit in the result > bitmap. The server MUST return an error if it supports an > attribute on the target but cannot obtain its value. In that case, > no attribute values will be returned. Further, RFC 9754 Section 5 states: > These new attributes are invalid to be used with GETATTR, VERIFY, > and NVERIFY, and they can only be used with CB_GETATTR and SETATTR > by a client holding an appropriate delegation. Thus there does not appear to be a specific server response mandated by specification. Taking the guidance that querying these attributes via GETATTR is "invalid", NFSD will return nfserr_inval, failing the request entirely.
References
Impacted products
Vendor Product Version
Linux Linux Version: 51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b
Version: 51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "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": "d8f3f94dc950e7c62c96af432c26745885b0a18a",
              "status": "affected",
              "version": "51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b",
              "versionType": "git"
            },
            {
              "lessThan": "4f76435fd517981f01608678c06ad9718a86ee98",
              "status": "affected",
              "version": "51c0d4f7e317d3cb4a3001e502bd8ca2d57f2a4b",
              "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": "6.14"
            },
            {
              "lessThan": "6.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.8",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "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: Define actions for the new time_deleg FATTR4 attributes\n\nNFSv4 clients won\u0027t send legitimate GETATTR requests for these new\nattributes because they are intended to be used only with CB_GETATTR\nand SETATTR. But NFSD has to do something besides crashing if it\never sees a GETATTR request that queries these attributes.\n\nRFC 8881 Section 18.7.3 states:\n\n\u003e The server MUST return a value for each attribute that the client\n\u003e requests if the attribute is supported by the server for the\n\u003e target file system. If the server does not support a particular\n\u003e attribute on the target file system, then it MUST NOT return the\n\u003e attribute value and MUST NOT set the attribute bit in the result\n\u003e bitmap. The server MUST return an error if it supports an\n\u003e attribute on the target but cannot obtain its value. In that case,\n\u003e no attribute values will be returned.\n\nFurther, RFC 9754 Section 5 states:\n\n\u003e These new attributes are invalid to be used with GETATTR, VERIFY,\n\u003e and NVERIFY, and they can only be used with CB_GETATTR and SETATTR\n\u003e by a client holding an appropriate delegation.\n\nThus there does not appear to be a specific server response mandated\nby specification. Taking the guidance that querying these attributes\nvia GETATTR is \"invalid\", NFSD will return nfserr_inval, failing the\nrequest entirely."
        }
      ],
      "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 vulnerable code is the NFSv4 server (nfsd) XDR encoder, reached purely by processing an NFSv4.2 COMPOUND received over TCP port 2049 from a remote client. No local access to the server is required.\nAC:L - The attacker deterministically triggers the NULL function-pointer call by setting bit 84 or 85 in the GETATTR (or READDIR/VERIFY) attribute bitmap; there is no race, no memory-layout dependency, and the config is the default NFSv4.2 server build.\nPR:N - NFS AUTH_SYS/AUTH_NULL verifies no credentials \u2014 the attacker merely issues EXCHANGE_ID/CREATE_SESSION and then PUTROOTFH+GETATTR, with `fh_verify(..., NFSD_MAY_NOP)` performing no permission check, so no authenticated principal is needed against an exported server.\nUI:N - The attacker sends the malformed GETATTR request unilaterally; no action by any administrator or user on the server or on a legitimate client is needed.\nS:U - The crash occurs in the nfsd kernel thread within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:N - The call to the NULL slot faults before any attribute bytes are encoded and the partial reply is discarded via xdr_truncate_encode(), so no kernel memory contents are disclosed.\nI:N - No out-of-bounds write or type confusion occurs; the indirect call to address 0 faults immediately and a remote attacker cannot map page 0 to gain control flow, so no data or code is modified.\nA:H - Dereferencing the NULL function pointer oopses the nfsd service thread (or panics the machine with panic_on_oops), and the unauthenticated request can be replayed to kill every nfsd thread, taking the file server completely offline."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:09:38.372Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d8f3f94dc950e7c62c96af432c26745885b0a18a"
        },
        {
          "url": "https://git.kernel.org/stable/c/4f76435fd517981f01608678c06ad9718a86ee98"
        }
      ],
      "title": "NFSD: Define actions for the new time_deleg FATTR4 attributes",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40326",
    "datePublished": "2025-12-08T00:46:53.212Z",
    "dateReserved": "2025-04-16T07:20:57.186Z",
    "dateUpdated": "2026-08-05T12:09:38.372Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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