CVE-2025-38338

Estado: AnalizadaAlta (7.8)—

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

fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()

Sometimes, when a file was read while it was being truncated by another NFS client, the kernel could deadlock because folio_unlock() was called twice, and the second call would XOR back the `PG_locked` flag.

Most of the time (depending on the timing of the truncation), nobody notices the problem because folio_unlock() gets called three times, which flips `PG_locked` back off:

The problem is that nfs_read_add_folio() is not supposed to unlock the folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is missing in nfs_return_empty_folio().

Leer descripción completaMostrar menos

Rarely this leads to a warning in netfs_read_collection():

Most of the time, however, processes just get stuck forever in folio_wait_bit_common(), waiting for `PG_locked` to disappear, which never happens because nobody is really holding the folio lock.

Detalles técnicos trazas, registros y código del informe original

 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio,
    nfs_return_empty_folio
 2. vfs_read, nfs_read_folio, ... netfs_read_collection,
    netfs_unlock_abandoned_read_pages
 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,
    nfs_return_empty_folio

 ------------[ cut here ]------------
 R=0000031c: folio 10 is not locked
 WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00
 [...]
 Workqueue: events_unbound netfs_read_collection_worker
 RIP: 0010:netfs_read_collection+0x7c0/0xf00
 [...]
 Call Trace:
  <TASK>
  netfs_read_collection_worker+0x67/0x80
  process_one_work+0x12e/0x2c0
  worker_thread+0x295/0x3a0

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.17%
Percentil entre todas las CVEs puntuadas: 6
Fecha de la puntuación: 5/10/2026

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.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation45 %
Impacto principalT1499.004 Application or System Exploitationimpact70 %
Impacto secundarioT1078 Valid Accountsstealth · persistence · privilege escalation · initial access35 %

CWE-415 (doble liberación) en kernel NFS con AV:L/PR:L. Aunque la vulnerabilidad es un bug de sincronización (deadlock), la explotación requiere acceso local con permisos limitados. El impacto principal es denegación de servicio (proceso bloqueado indefinidamente); secundariamente, desde ese context

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

Application Developer Guidance Active Directory Configuration User Training User Account Management Threat Intelligence Program Privileged Account Management

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-415

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2025-38338",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "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": "000dbe0bec058cbf2ca9e156e4a5584f5158b0f9",
              "lessThan": "14f5549ad163be2c018abc1bb38370fff617a243",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "000dbe0bec058cbf2ca9e156e4a5584f5158b0f9",
              "lessThan": "5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "000dbe0bec058cbf2ca9e156e4a5584f5158b0f9",
              "lessThan": "1e93b61d3eaa14bfebcc2716ac09d43f3845d420",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "000dbe0bec058cbf2ca9e156e4a5584f5158b0f9",
              "lessThan": "4c10fa44bc5f700e2ea21de2fbae520ba21f19d9",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/nfs/read.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.4",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.6.95",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.35",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.15.4",
              "versionType": "semver",
              "lessThanOrEqual": "6.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.16",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/nfs/read.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2025-07-10T09:15:28.510",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/14f5549ad163be2c018abc1bb38370fff617a243",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/1e93b61d3eaa14bfebcc2716ac09d43f3845d420",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/4c10fa44bc5f700e2ea21de2fbae520ba21f19d9",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/5bf0b9eeb0174686f22c2e5b8fb9f47ad25da6f5",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-415"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()\n\nSometimes, when a file was read while it was being truncated by\nanother NFS client, the kernel could deadlock because folio_unlock()\nwas called twice, and the second call would XOR back the `PG_locked`\nflag.\n\nMost of the time (depending on the timing of the truncation), nobody\nnotices the problem because folio_unlock() gets called three times,\nwhich flips `PG_locked` back off:\n\n 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio,\n    nfs_return_empty_folio\n 2. vfs_read, nfs_read_folio, ... netfs_read_collection,\n    netfs_unlock_abandoned_read_pages\n 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,\n    nfs_return_empty_folio\n\nThe problem is that nfs_read_add_folio() is not supposed to unlock the\nfolio if fscache is enabled, and a nfs_netfs_folio_unlock() check is\nmissing in nfs_return_empty_folio().\n\nRarely this leads to a warning in netfs_read_collection():\n\n ------------[ cut here ]------------\n R=0000031c: folio 10 is not locked\n WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00\n [...]\n Workqueue: events_unbound netfs_read_collection_worker\n RIP: 0010:netfs_read_collection+0x7c0/0xf00\n [...]\n Call Trace:\n  <TASK>\n  netfs_read_collection_worker+0x67/0x80\n  process_one_work+0x12e/0x2c0\n  worker_thread+0x295/0x3a0\n\nMost of the time, however, processes just get stuck forever in\nfolio_wait_bit_common(), waiting for `PG_locked` to disappear, which\nnever happens because nobody is really holding the folio lock."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: fs/nfs/read: corrige error de doble desbloqueo en nfs_return_empty_folio() En ocasiones, cuando se leía un archivo mientras otro cliente NFS lo estaba truncando, el kernel podía bloquearse porque se llamaba a folio_unlock() dos veces y la segunda llamada XOR devolvería el indicador `PG_locked`. La mayoría de las veces (dependiendo del momento del truncamiento), nadie nota el problema porque folio_unlock() se llama tres veces, lo que desactiva `PG_locked`: 1. vfs_read, nfs_read_folio, ... nfs_read_add_folio, nfs_return_empty_folio 2. vfs_read, nfs_read_folio, ... netfs_read_collection, netfs_unlock_abandoned_read_pages 3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio, nfs_return_empty_folio El problema es que nfs_read_add_folio() no debe desbloquear el folio si fscache está habilitado, y falta una comprobación nfs_netfs_folio_unlock() en nfs_return_empty_folio(). En raras ocasiones, esto genera una advertencia en netfs_read_collection(): ------------[ cortar aquí ]------------ R=0000031c: el folio 10 no está bloqueado ADVERTENCIA: CPU: 0 PID: 29 en fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00 [...] Cola de trabajo: events_unbound netfs_read_collection_worker RIP: 0010:netfs_read_collection+0x7c0/0xf00 [...] Rastreo de llamadas:  netfs_read_collection_worker+0x67/0x80 process_one_work+0x12e/0x2c0worker_thread+0x295/0x3a0 Sin embargo, la mayoría de las veces, los procesos simplemente se quedan atascados para siempre en folio_wait_bit_common(), esperando que `PG_locked` desaparezca, lo que nunca sucede porque nadie está realmente reteniendo el cerradura de folio. "
    }
  ],
  "lastModified": "2026-06-17T09:16:39.273",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "F17A70D5-5B72-4411-9C16-98EF57D0C931",
              "versionEndExcluding": "6.6.95",
              "versionStartIncluding": "6.4"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E569FD34-0076-4428-BE17-EECCF867611C",
              "versionEndExcluding": "6.12.35",
              "versionStartIncluding": "6.7"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DFD174C5-1AA2-4671-BDDC-1A9FCC753655",
              "versionEndExcluding": "6.15.4",
              "versionStartIncluding": "6.13"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}