CVE-2026-99083

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix heap out-of-bounds write in krb5_authenticate() In krb5_authenticate(), out_len is calculated to determine available headroom in response_buf for the incoming Kerberos AP-REP token. However, when SMB2_SESSION_SETUP is processed as a non-first element of a compounded SMB2 request, the calculation omits work->next_smb2_rsp_hdr_off. This causes out_len to overstate remaining buffer headroom by the cumulative size of prior responses in the compound chain. Consequently, the length check in ksmbd_krb5_authenticate() (*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy() to write the AP-REP blob past the end of response_buf into adjacent kernel heap memory. Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.

Severity

HIGH

CVSS score

8.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-10-23 13:17:32.577000

Last modified

2026-10-30 13:21:44.380000

View original CVE JSON

{
  "id": "CVE-2026-99083",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-10-23T13:17:32.577",
  "lastModified": "2026-10-30T13:21:44.380",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix heap out-of-bounds write in krb5_authenticate()\n\nIn krb5_authenticate(), out_len is calculated to determine available\nheadroom in response_buf for the incoming Kerberos AP-REP token. However,\nwhen SMB2_SESSION_SETUP is processed as a non-first element of a compounded\nSMB2 request, the calculation omits work->next_smb2_rsp_hdr_off.\n\nThis causes out_len to overstate remaining buffer headroom by\nthe cumulative size of prior responses in the compound chain. Consequently,\nthe length check in ksmbd_krb5_authenticate()\n(*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy()\nto write the AP-REP blob past the end of response_buf into adjacent kernel\nheap memory.\n\nFix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len,\nensuring it accurately reflects physical remaining buffer space."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "676392184785ace61e939831e7ca44a03d438c3b",
              "lessThan": "a07dfb33112a42437f9d2d0bfd35c68575257381",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "ef572ffa8eb44111eed2925fbb2adca78bdcbf61",
              "lessThan": "1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8",
              "lessThan": "59c6dcc5dd9dafe764ca0d40525933b2be69b059",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8",
              "lessThan": "80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8",
              "lessThan": "517404e157395d0f8da125ca956c566895dfcd06",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8",
              "lessThan": "4722d06b2907585074252061b1024a696c1cfc23",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8",
              "lessThan": "23a0be6a84a38ac169eeab49017934e8e27c65f0",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2ba03cecb12ac7ac9e0170e251543c56832d9959",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "5.15.145",
              "lessThan": "5.15.224",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "6.1.40",
              "lessThan": "6.1.191",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "6.4.5",
              "lessThan": "6.5",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "6.5",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "6.5",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.224",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.114",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.58",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.12",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/23a0be6a84a38ac169eeab49017934e8e27c65f0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
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      "url": "https://git.kernel.org/stable/c/4722d06b2907585074252061b1024a696c1cfc23",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/517404e157395d0f8da125ca956c566895dfcd06",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/59c6dcc5dd9dafe764ca0d40525933b2be69b059",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a07dfb33112a42437f9d2d0bfd35c68575257381",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}