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CVE-2026-89677

Estado: RecibidaCrítica (9.8)—

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

nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()

dentry_create() can hypothetically provide a different dentry than the one passed in. This could happen, for example, if the exported filesystem is NFS, and the server returned to OPEN a filehandle which matched a directory that was already in the dcache. Clearly this would not be expected!

If this were to happen the dentry (child) that was already stored in resfhp could be freed and later dereferenced.

We shouldn't call fh_compose() until we are certain that we have the final dentry, so this patch moved the fh_compose() call to two places: one for the case where the target already exists, and one after dentry_create() where it was created.

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 crítica en kernel Linux (AV:N/AC:L/PR:N) explotable remotamente vía NFSD. Permite escalada de privilegios (manipulación de dentry) o denegación de servicio por desreferencia de memoria liberada.

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 TrafficApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareVulnerability ScanningThreat Intelligence Program

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-2026-89677",
  "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": "64a989dbd144e0622371396461b11335459692d2",
              "lessThan": "033e783709ce99662cf81f6abcad746a8da9d35f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "64a989dbd144e0622371396461b11335459692d2",
              "lessThan": "3e2c79360c6a89975ec5b5a7d4ef937e4db91a27",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "7.0",
              "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/nfsd/nfs4proc.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:19:54.393",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/033e783709ce99662cf81f6abcad746a8da9d35f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/3e2c79360c6a89975ec5b5a7d4ef937e4db91a27",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()\n\ndentry_create() can hypothetically provide a different dentry than the\none passed in.  This could happen, for example, if the exported\nfilesystem is NFS, and the server returned to OPEN a filehandle which\nmatched a directory that was already in the dcache.  Clearly this would\nnot be expected!\n\nIf this were to happen the dentry (child) that was already stored in\nresfhp could be freed and later dereferenced.\n\nWe shouldn't call fh_compose() until we are certain that we have the\nfinal dentry, so this patch moved the fh_compose() call to two places:\none for the case where the target already exists, and one after\ndentry_create() where it was created."
    }
  ],
  "lastModified": "2026-09-13T07:17:33.423",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}