CVE-2026-89630

Estado: RecibidaCrítica (9.1)—

In the Linux kernel, the following vulnerability has been resolved:

smb: client: restore the data_offset bound in is_valid_oplock_break()

Commit 83bfbd0bb902 ("cifs: Remove the RFC1002 header from smb_hdr") changed the quantity this bound is measured against. It used to be srv->total_read minus the 4-byte RFC1002 preamble that total_read then included, so it was the SMB message length. The same commit stopped counting the preamble, and the mechanical substitution to srv->total_read - srv->pdu_size left an expression that is identically zero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly pdu_length - MID_HEADER_SIZE() more, adding both to total_read.

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len is therefore 0, the subtraction below it wraps, and no __u32 DataOffset can exceed the result, so the check from commit 097f5863b1a0 ("cifs: read overflow in is_valid_oplock_break()") no longer rejects anything. Use total_read, which is now the message length on its own.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Puntuación base: 9.1

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.54%
Percentil entre todas las CVEs puntuadas: 43
Fecha de la puntuación: 6/10/2026

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 access75 %
Impacto principalT1005 Data from Local Systemcollection70 %
Impacto secundarioT1499.004 Application or System Exploitationimpact65 %

Vulnerabilidad de lectura en buffer del cliente SMB (CIFS) en kernel Linux sin autenticación requerida (PR:N, UI:N). Vector CVSS muestra acceso remoto (AV:N) con alto impacto en confidencialidad (C:H) e impacto en disponibilidad (A:H); permite explotación remota (T1190) con potencial lectura de dato

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 Privileged Account Management Network Segmentation Limit Access to Resource Over Network Application Isolation and Sandboxing

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-2026-89630",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.1,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "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": "83bfbd0bb9025f98fa62b44f93bd67466773d1db",
              "lessThan": "5b16a1967a01ad4496a7206a87c3eb16f1df2b05",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "83bfbd0bb9025f98fa62b44f93bd67466773d1db",
              "lessThan": "ba22f575de9deeae4ae0859ca4315a7698226237",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/smb/client/smb1misc.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.19",
              "versionType": "semver"
            },
            {
              "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/smb1misc.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:19:48.517",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237",
      "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: restore the data_offset bound in is_valid_oplock_break()\n\nCommit 83bfbd0bb902 (\"cifs: Remove the RFC1002 header from smb_hdr\")\nchanged the quantity this bound is measured against.  It used to be\nsrv->total_read minus the 4-byte RFC1002 preamble that total_read then\nincluded, so it was the SMB message length.  The same commit stopped\ncounting the preamble, and the mechanical substitution to\nsrv->total_read - srv->pdu_size left an expression that is identically\nzero: standard_receive3() reads MID_HEADER_SIZE() bytes and then exactly\npdu_length - MID_HEADER_SIZE() more, adding both to total_read.\n\nlen is therefore 0, the subtraction below it wraps, and no __u32\nDataOffset can exceed the result, so the check from commit 097f5863b1a0\n(\"cifs: read overflow in is_valid_oplock_break()\") no longer rejects\nanything.  Use total_read, which is now the message length on its own."
    }
  ],
  "lastModified": "2026-09-13T07:17:28.067",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}