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CVE-2026-89641

Estado: RecibidaAlta (7.8)—

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

cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()

When the else branch of cifs_file_set_size() finds a writable file handle via find_writable_file(), it borrows tcon and server from the handle's tlink, attempts the handle-based set_file_size() RPC, and then releases the handle with cifsFileInfo_put().

If set_file_size() fails, execution falls through to the path-based fallback, which reuses the borrowed tcon and server under the "if (tcon == NULL)" guard.

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Since tcon is not NULL at that point, the guard is skipped. If cifsFileInfo_put() dropped the last reference on a tlink that was already removed from the tlink tree (TCON_LINK_IN_TREE cleared, as happens during reconnection or session teardown), cifs_put_tlink() will have freed tcon; the subsequent set_path_size() call is then a use-after-free.

Setting tcon = NULL after cifsFileInfo_put() causes the existing guard to take the cifs_sb_tlink() path, which acquires a fresh reference for the path-based operation or fails cleanly if the session is gone.

CVSS

Probabilidad de explotación (EPSS)

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.

Vulnerabilidad de use-after-free en kernel Linux que requiere acceso local (AV:L, PR:L), causando denegación de servicio o lectura de memoria del kernel.

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

Threat Intelligence ProgramFilter Network TrafficExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate Software

Tecnologías afectadas (1)

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

Linux — Linux KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-89641",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "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": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "4bea15d9c7683218f57b8c1f5f0aa75cab76af8d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "110fee6b9bb58a5c50047fc2594d415f741b591e",
              "lessThan": "b96db32fed8dfb2478d7c208f89bf383beed1535",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/smb/client/inode.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.18",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.18.50",
              "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/inode.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:19:49.867",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()\n\nWhen the else branch of cifs_file_set_size() finds a writable file handle\nvia find_writable_file(), it borrows tcon and server from the handle's\ntlink, attempts the handle-based set_file_size() RPC, and then releases\nthe handle with cifsFileInfo_put().\n\nIf set_file_size() fails, execution falls through to the path-based\nfallback, which reuses the borrowed tcon and server under the\n\"if (tcon == NULL)\" guard.  Since tcon is not NULL at that point, the\nguard is skipped.  If cifsFileInfo_put() dropped the last reference on a\ntlink that was already removed from the tlink tree (TCON_LINK_IN_TREE\ncleared, as happens during reconnection or session teardown),\ncifs_put_tlink() will have freed tcon; the subsequent set_path_size()\ncall is then a use-after-free.\n\nSetting tcon = NULL after cifsFileInfo_put() causes the existing guard\nto take the cifs_sb_tlink() path, which acquires a fresh reference for\nthe path-based operation or fails cleanly if the session is gone."
    }
  ],
  "lastModified": "2026-09-13T07:17:29.377",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}