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CVE-2026-18500

Estado: AnalizadaAlta (8.1)—

@fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use different keys for different authorization domains, for example separate user and admin keys, therefore accept a token signed with the global key on a route that explicitly requires another key. This lets an ordinary authenticated user cross a key-based trust boundary without knowing either secret. The issue is fixed in @fastify/jwt 10.2.2, where an explicit per-call key takes precedence over the global secret. Users should upgrade to 10.2.2.

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 en autenticación JWT (CWE-347): atacante autenticado (PR:L) explota fallo de precedencia de claves para eludir controles de autorización y obtener acceso a dominios distintos sin conocer las claves. Red sin privilegios iniciales requiere autenticación previa (PR:L).

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

Privileged Account ManagementMulti-factor AuthenticationVulnerability ScanningUser TrainingThreat Intelligence ProgramPrivileged Process Integrity

Tecnologías afectadas (1)

Fastify — Fastify/jwt

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-18500",
  "cveTags": [],
  "metrics": {
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          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-17T19:45:28.953645Z"
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          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
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      "affectedData": [
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              "versionType": "semver"
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  "published": "2026-08-15T14:17:07.473",
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      "url": "https://cna.openjsf.org/security-advisories.html",
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        "Vendor Advisory"
      ],
      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
    },
    {
      "url": "https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg",
      "tags": [
        "Mitigation",
        "Vendor Advisory"
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      "source": "ce714d77-add3-4f53-aff5-83d477b104bb"
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  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "source": "ce714d77-add3-4f53-aff5-83d477b104bb",
      "description": [
        {
          "lang": "en",
          "value": "CWE-347"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "@fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use different keys for different authorization domains, for example separate user and admin keys, therefore accept a token signed with the global key on a route that explicitly requires another key. This lets an ordinary authenticated user cross a key-based trust boundary without knowing either secret. The issue is fixed in @fastify/jwt 10.2.2, where an explicit per-call key takes precedence over the global secret. Users should upgrade to 10.2.2."
    }
  ],
  "lastModified": "2026-09-04T13:17:20.220",
  "configurations": [
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}