FKIE_CVE-2026-68431

Vulnerability from fkie_nvd - Published: 2026-08-12 00:17 - Updated: 2026-08-23 13:16
Severity
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate minimum PDU size for transform requests The receive path applies the minimum SMB2 PDU size check only when ProtocolId is SMB2_PROTO_NUMBER. A packet carrying SMB2_TRANSFORM_PROTO_NUM bypasses the check even when the negotiated dialect does not provide transform handling. On an SMB 2.1 connection, a short transform packet therefore reaches init_smb2_rsp_hdr(), which interprets the request as a full SMB2 header and reads beyond the request allocation. The copied fields can then be returned to the unauthenticated client. Compression transforms are converted to ordinary SMB2 messages before protocol validation. After that conversion, validate ordinary SMB2 requests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption transform requests to contain both a transform header and an SMB2 header. This rejects truncated requests before work allocation.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/22f1aa35b87e471cc31b35b74451f46630863b12
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/32e486b70c256d5ef4baa5a2936ade2fea50e8eb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/928dda88d0e13fbca381255028f65b244343a4ea
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b62c510f59803f82f9b4c76ead2a56833b2984c7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cfc0b8e5080aec87700774e8568765eaa4b7b92b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d8e5c5672724b8f3c4c099d2cf60239c996e5424
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d9e9753dfd43bd27c956578df7804a3c90b80fdc
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "22f1aa35b87e471cc31b35b74451f46630863b12",
              "status": "affected",
              "version": "df3a4518aee64f21bcafa891105b468413f27431",
              "versionType": "git"
            },
            {
              "lessThan": "928dda88d0e13fbca381255028f65b244343a4ea",
              "status": "affected",
              "version": "543c12c2644e772caa6880662c2a852cfdc5a10c",
              "versionType": "git"
            },
            {
              "lessThan": "d8e5c5672724b8f3c4c099d2cf60239c996e5424",
              "status": "affected",
              "version": "368ba06881c395f1c9a7ba22203cf8d78b4addc0",
              "versionType": "git"
            },
            {
              "lessThan": "32e486b70c256d5ef4baa5a2936ade2fea50e8eb",
              "status": "affected",
              "version": "368ba06881c395f1c9a7ba22203cf8d78b4addc0",
              "versionType": "git"
            },
            {
              "lessThan": "d9e9753dfd43bd27c956578df7804a3c90b80fdc",
              "status": "affected",
              "version": "368ba06881c395f1c9a7ba22203cf8d78b4addc0",
              "versionType": "git"
            },
            {
              "lessThan": "b62c510f59803f82f9b4c76ead2a56833b2984c7",
              "status": "affected",
              "version": "368ba06881c395f1c9a7ba22203cf8d78b4addc0",
              "versionType": "git"
            },
            {
              "lessThan": "cfc0b8e5080aec87700774e8568765eaa4b7b92b",
              "status": "affected",
              "version": "368ba06881c395f1c9a7ba22203cf8d78b4addc0",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e9cb7be2fcbaee9e808b729e92948d38d52e5add",
              "versionType": "git"
            },
            {
              "lessThan": "5.15.217",
              "status": "affected",
              "version": "5.15.145",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.184",
              "status": "affected",
              "version": "6.1.34",
              "versionType": "semver"
            },
            {
              "lessThan": "6.4",
              "status": "affected",
              "version": "6.3.8",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/connection.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.217",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.184",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.153",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.105",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.46",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "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\nksmbd: validate minimum PDU size for transform requests\n\nThe receive path applies the minimum SMB2 PDU size check only when\nProtocolId is SMB2_PROTO_NUMBER. A packet carrying\nSMB2_TRANSFORM_PROTO_NUM bypasses the check even when the negotiated\ndialect does not provide transform handling.\n\nOn an SMB 2.1 connection, a short transform packet therefore reaches\ninit_smb2_rsp_hdr(), which interprets the request as a full SMB2 header\nand reads beyond the request allocation. The copied fields can then be\nreturned to the unauthenticated client.\n\nCompression transforms are converted to ordinary SMB2 messages before\nprotocol validation. After that conversion, validate ordinary SMB2\nrequests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption\ntransform requests to contain both a transform header and an SMB2\nheader. This rejects truncated requests before work allocation."
    }
  ],
  "id": "CVE-2026-68431",
  "lastModified": "2026-08-23T13:16:36.823",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-12T00:17:43.180",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/22f1aa35b87e471cc31b35b74451f46630863b12"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/32e486b70c256d5ef4baa5a2936ade2fea50e8eb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/928dda88d0e13fbca381255028f65b244343a4ea"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b62c510f59803f82f9b4c76ead2a56833b2984c7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cfc0b8e5080aec87700774e8568765eaa4b7b92b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d8e5c5672724b8f3c4c099d2cf60239c996e5424"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d9e9753dfd43bd27c956578df7804a3c90b80fdc"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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