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CVE-2026-89705

Estado: RecibidaAlta (7.1)—

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

nfsd: restore rq_status_counter to even on all nfsd_dispatch() exit paths

nfsd_dispatch() sets rq_status_counter to an odd value once a request has been decoded, and back to an even value once it has been fully processed, forming a seq-lock like protocol with the lockless reader in nfsd_nl_rpc_status_get_dumpit().

Only the fully successful path restored the counter to even. The cache-hit (RC_REPLY), drop (RC_DROPIT / RQ_DROPME) and encode-error paths all return after the odd-valued store without ever bringing the counter back to even. Once one of those paths is taken, rq_status_counter is left odd: the next request's decode ORs in 1 (still odd) and only a subsequent successful encode restores even. While stuck odd, the dumpit reader treats the rqstp fields as stable and its retry check compares against the same unchanging odd value, so it never detects concurrent mutation. This exposes actively mutating fields (e.g. args->ops / args->opcnt during compound decode and release) to the lockless reader, which can read past the end of the 8-element inline ops array.

Leer descripción completaMostrar menos

Add a helper that advances the counter to the next even value and call it on every return path that follows the odd-valued store. The decode-error path is left untouched as it is reached before the counter is set odd.

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 local (AV:L, PR:L) que permite lectura de memoria del kernel (C:H) y DoS (A:H) sin interacción. El atacante con privilegios locales explota una condición de carrera en nfsd_dispatch() para leer datos inestables, priorizando acceso a información (T1005) sobre disponibilidad.

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-2026-89705",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.1,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "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": "bd9d6a3efa9709e653aafbeb859289feccb8e70c",
              "lessThan": "b08c30f08d57f30699d36809d92f0b683dca261f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "bd9d6a3efa9709e653aafbeb859289feccb8e70c",
              "lessThan": "f6045886fe3f14f269f683d64021b004a50d0efa",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "fs/nfsd/nfssvc.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.7"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.7",
              "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/nfssvc.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:19:57.780",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/b08c30f08d57f30699d36809d92f0b683dca261f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/f6045886fe3f14f269f683d64021b004a50d0efa",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: restore rq_status_counter to even on all nfsd_dispatch() exit paths\n\nnfsd_dispatch() sets rq_status_counter to an odd value once a request has\nbeen decoded, and back to an even value once it has been fully processed,\nforming a seq-lock like protocol with the lockless reader in\nnfsd_nl_rpc_status_get_dumpit().\n\nOnly the fully successful path restored the counter to even. The cache-hit\n(RC_REPLY), drop (RC_DROPIT / RQ_DROPME) and encode-error paths all return\nafter the odd-valued store without ever bringing the counter back to even.\nOnce one of those paths is taken, rq_status_counter is left odd: the next\nrequest's decode ORs in 1 (still odd) and only a subsequent successful\nencode restores even. While stuck odd, the dumpit reader treats the rqstp\nfields as stable and its retry check compares against the same unchanging\nodd value, so it never detects concurrent mutation. This exposes actively\nmutating fields (e.g. args->ops / args->opcnt during compound decode and\nrelease) to the lockless reader, which can read past the end of the\n8-element inline ops array.\n\nAdd a helper that advances the counter to the next even value and call it\non every return path that follows the odd-valued store. The decode-error\npath is left untouched as it is reached before the counter is set odd."
    }
  ],
  "lastModified": "2026-09-13T07:17:36.127",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}