FKIE_CVE-2025-40212

Vulnerability from fkie_nvd - Published: 2025-11-24 13:16 - Updated: 2026-10-18 20:10
Severity
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix refcount leak in nfsd_set_fh_dentry() nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find the various exported filesystems using LOOKUP requests from a known root filehandle. NFSv3 uses the MOUNT protocol to find those exported filesystems and so is not given access to the pseudo root filesystem. If a v3 (or v2) client uses a filehandle from that filesystem, nfsd_set_fh_dentry() will report an error, but still stores the export in "struct svc_fh" even though it also drops the reference (exp_put()). This means that when fh_put() is called an extra reference will be dropped which can lead to use-after-free and possible denial of service. Normal NFS usage will not provide a pseudo-root filehandle to a v3 client. This bug can only be triggered by the client synthesising an incorrect filehandle. To fix this we move the assignments to the svc_fh later, after all possible error cases have been detected.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b6bc86ce3944b10b9fc181fc00c1a520a20ed965
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfsfh.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b6bc86ce3944b10b9fc181fc00c1a520a20ed965",
              "status": "affected",
              "version": "ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444",
              "versionType": "git"
            },
            {
              "lessThan": "c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2",
              "status": "affected",
              "version": "ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444",
              "versionType": "git"
            },
            {
              "lessThan": "8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c",
              "status": "affected",
              "version": "ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfsfh.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
            {
              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.59",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix refcount leak in nfsd_set_fh_dentry()\n\nnfsd exports a \"pseudo root filesystem\" which is used by NFSv4 to find\nthe various exported filesystems using LOOKUP requests from a known root\nfilehandle.  NFSv3 uses the MOUNT protocol to find those exported\nfilesystems and so is not given access to the pseudo root filesystem.\n\nIf a v3 (or v2) client uses a filehandle from that filesystem,\nnfsd_set_fh_dentry() will report an error, but still stores the export\nin \"struct svc_fh\" even though it also drops the reference (exp_put()).\nThis means that when fh_put() is called an extra reference will be dropped\nwhich can lead to use-after-free and possible denial of service.\n\nNormal NFS usage will not provide a pseudo-root filehandle to a v3\nclient.  This bug can only be triggered by the client synthesising an\nincorrect filehandle.\n\nTo fix this we move the assignments to the svc_fh later, after all\npossible error cases have been detected."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnfsd: corregir fuga de contador de referencias en nfsd_set_fh_dentry()\n\nnfsd exporta un \u0027pseudo sistema de archivos ra\u00edz\u0027 que es utilizado por NFSv4 para encontrar los diversos sistemas de archivos exportados usando solicitudes LOOKUP desde un filehandle ra\u00edz conocido. NFSv3 utiliza el protocolo MOUNT para encontrar esos sistemas de archivos exportados y por lo tanto no se le da acceso al pseudo sistema de archivos ra\u00edz.\n\nSi un cliente v3 (o v2) utiliza un filehandle de ese sistema de archivos, nfsd_set_fh_dentry() reportar\u00e1 un error, pero a\u00fan almacena la exportaci\u00f3n en \u0027struct svc_fh\u0027 a pesar de que tambi\u00e9n libera la referencia (exp_put()). Esto significa que cuando se llama a fh_put(), se liberar\u00e1 una referencia adicional, lo que puede llevar a uso despu\u00e9s de liberaci\u00f3n y posible denegaci\u00f3n de servicio.\n\nEl uso normal de NFS no proporcionar\u00e1 un filehandle pseudo-ra\u00edz a un cliente v3. Este error solo puede ser desencadenado por el cliente sintetizando un filehandle incorrecto.\n\nPara corregir esto, movemos las asignaciones al svc_fh m\u00e1s tarde, despu\u00e9s de que se hayan detectado todos los posibles casos de error."
    }
  ],
  "id": "CVE-2025-40212",
  "lastModified": "2026-10-18T20:10:00.110",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2025-11-24T13:16:02.813",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b6bc86ce3944b10b9fc181fc00c1a520a20ed965"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}



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