CVE-2026-89633

Estado: RecibidaCrítica (9.8)—

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:

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.

Leer descripción completaMostrar menos

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.

Detalles técnicos trazas, registros y código del informe original

  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);

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 9.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.65%
Percentil entre todas las CVEs puntuadas: 49
Fecha de la puntuación: 5/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access85 %
Impacto principalT1565.001 Stored Data Manipulationimpact75 %
Impacto secundarioT1005 Data from Local Systemcollection80 %
Impacto secundarioT1499.004 Application or System Exploitationimpact70 %

Vulnerabilidad de lectura/escritura fuera de límites (OOB) en SMB client del kernel Linux. Vector CVSS de red sin autenticación (AV:N/PR:N/UI:N) indica T1190. Impactos: manipulación de datos por sobrescritura de campos, lectura no autorizada de memoria heap, y potencial negación de servicio por corr

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network Traffic Vulnerability Scanning Restrict File and Directory Permissions Privileged Account Management Remote Data Storage Network Segmentation

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-89633",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "033bc80019f07d158630df4e69b19a49010f54f1",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e4eb295d38b57f4d4b956942a48887eb252d97c6",
              "lessThan": "6343c1da561962688f203362d80d6a3bfa39fa1b",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/smb/client/smb1transport.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver",
              "lessThanOrEqual": "7.2.*"
            },
            {
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/smb/client/smb1transport.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:19:48.887",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1",
      "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"
    }
  ],
  "vulnStatus": "Received",
  "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."
    }
  ],
  "lastModified": "2026-09-13T07:17:28.413",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}