CVE-2025-40212
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.
Leer descripción completaMostrar menos
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.
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: 0.40%
- Percentil entre todas las CVEs puntuadas: 32
- 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.
- Explotación
T1190Exploit Public-Facing Applicationinitial access75 % - Impacto principal
T1499.004Application or System Exploitationimpact70 %
Vulnerabilidad remota sin autenticación (AV:N, PR:N, UI:N) en servicio NFS expuesto; refcount leak causa DoS y potencial use-after-free con privilegios 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
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
Mostrar
{
"id": "CVE-2025-40212",
"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": "ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444",
"lessThan": "b6bc86ce3944b10b9fc181fc00c1a520a20ed965",
"versionType": "git"
},
{
"status": "affected",
"version": "ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444",
"lessThan": "c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2",
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{
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"lessThan": "8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c",
"versionType": "git"
}
],
"programFiles": [
"fs/nfsd/nfsfh.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.59",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.17.9",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/nfsd/nfsfh.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2025-11-24T13:16:02.813",
"references": [
{
"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",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Deferred",
"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."
}
],
"lastModified": "2026-07-30T06:24:18.133",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}