CVE-2026-89633

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2() coalesce_t2() computes data pointers directly from server-supplied DataOffset fields with no validation against buffer bounds: data_area_of_tgt = (char *)&pSMBt->hdr.Protocol + get_unaligned_le16(&pSMBt->t2_rsp.DataOffset); data_area_of_src = (char *)&pSMBs->hdr.Protocol + get_unaligned_le16(&pSMBs->t2_rsp.DataOffset); data_area_of_tgt += total_in_tgt; ... memcpy(data_area_of_tgt, data_area_of_src, total_in_src); A small DataOffset can push a pointer below the actual byte area, overwriting header fields; a large one can push it past the buffer end, causing out-of-bounds heap reads (source) or writes (target). The BCC overflow guard does not prevent this: BCC reflects how much data is present, while DataOffset controls where in the buffer it starts. The "validate target area" comment present since the function was first written in 2005 was a placeholder that was never implemented. Add lower- and upper-bound checks for both data pointers before the memcpy, and before any target header fields are modified.

Severity

CRITICAL

CVSS score

9.8 (v3.1)

Vulnerability status

Received

Source identifier

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

Published

2026-09-11 20:19:48.887000

Last modified

2026-10-30 13:20:23.223000

View original CVE JSON

{
  "id": "CVE-2026-89633",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:48.887",
  "lastModified": "2026-10-30T13:20:23.223",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()\n\ncoalesce_t2() computes data pointers directly from server-supplied\nDataOffset fields with no validation against buffer bounds:\n\n  data_area_of_tgt = (char *)&pSMBt->hdr.Protocol +\n                     get_unaligned_le16(&pSMBt->t2_rsp.DataOffset);\n  data_area_of_src = (char *)&pSMBs->hdr.Protocol +\n                     get_unaligned_le16(&pSMBs->t2_rsp.DataOffset);\n  data_area_of_tgt += total_in_tgt;\n  ...\n  memcpy(data_area_of_tgt, data_area_of_src, total_in_src);\n\nA small DataOffset can push a pointer below the actual byte area,\noverwriting header fields; a large one can push it past the buffer\nend, causing out-of-bounds heap reads (source) or writes (target).\nThe BCC overflow guard does not prevent this: BCC reflects how much\ndata is present, while DataOffset controls where in the buffer it\nstarts.\n\nThe \"validate target area\" comment present since the function was\nfirst written in 2005 was a placeholder that was never implemented.\n\nAdd lower- and upper-bound checks for both data pointers before the\nmemcpy, and before any target header fields are modified."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/smb/client/smb1transport.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "f7baf60435129e3a5f3500a38e3cb4c3860deed7",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "9f3a7440731a34c89ad04fef6616f185acb28401",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "531ac35abd74fb5b4aec5e19543e832613a1789d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "6eb70b78e48b0031bd1a05fe1b58959a48e87739",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "36d01415d881d5326a0dd3384f781cd7e69aff2d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "033bc80019f07d158630df4e69b19a49010f54f1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "6343c1da561962688f203362d80d6a3bfa39fa1b",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/smb/client/smb1transport.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2.6.12",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.273",
              "lessThanOrEqual": "5.10.*",
              "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": "6.12.113",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.51",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "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:N/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/36d01415d881d5326a0dd3384f781cd7e69aff2d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/531ac35abd74fb5b4aec5e19543e832613a1789d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/6eb70b78e48b0031bd1a05fe1b58959a48e87739",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/9f3a7440731a34c89ad04fef6616f185acb28401",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/f7baf60435129e3a5f3500a38e3cb4c3860deed7",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}