FKIE_CVE-2026-22037

Vulnerability from fkie_nvd - Published: 2026-01-19 17:15 - Updated: 2026-01-26 15:05
Severity ?
8.4 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L
Summary
The @fastify/express plugin adds full Express compatibility to Fastify. A security vulnerability exists in @fastify/express prior to version 4.0.3 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. The vulnerability is caused by how @fastify/express matches requests against registered middleware paths. This vulnerability is similar to, but differs from, CVE-2026-22031 because this is a different npm module with its own code. Version 4.0.3 of @fastify/express contains a patch fort the issue.
References
security-advisories@github.comhttps://github.com/fastify/fastify-express/commit/dc02a3fe1387f945143f22597baa42557d549a40
security-advisories@github.comhttps://github.com/fastify/fastify-express/security/advisories/GHSA-g6q3-96cp-5r5m
Impacted products
Vendor Product Version
To clipboard 

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The @fastify/express plugin adds full Express compatibility to Fastify. A security vulnerability exists in @fastify/express prior to version 4.0.3 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. The vulnerability is caused by how @fastify/express matches requests against registered middleware paths. This vulnerability is similar to, but differs from, CVE-2026-22031 because this is a different npm module with its own code. Version 4.0.3 of @fastify/express contains a patch fort the issue."
    },
    {
      "lang": "es",
      "value": "El plugin @fastify/express a\u00f1ade compatibilidad completa con Express a Fastify. Existe una vulnerabilidad de seguridad en @fastify/express anterior a la versi\u00f3n 4.0.3 donde el middleware registrado con un prefijo de ruta espec\u00edfico puede ser eludido utilizando caracteres codificados en URL (p. ej., \u0027/%61dmin\u0027 en lugar de \u0027/admin\u0027). Mientras que el motor de middleware no logra coincidir con la ruta codificada y omite la ejecuci\u00f3n, el router subyacente de Fastify decodifica correctamente la ruta y coincide con el manejador de ruta, permitiendo a los atacantes acceder a puntos finales protegidos sin las restricciones del middleware. La vulnerabilidad es causada por c\u00f3mo @fastify/express compara las solicitudes con las rutas de middleware registradas. Esta vulnerabilidad es similar a, pero difiere de, CVE-2026-22031 porque este es un m\u00f3dulo npm diferente con su propio c\u00f3digo. La versi\u00f3n 4.0.3 de @fastify/express contiene un parche para el problema."
    }
  ],
  "id": "CVE-2026-22037",
  "lastModified": "2026-01-26T15:05:39.840",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 8.4,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 6.0,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-19T17:15:50.283",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify-express/commit/dc02a3fe1387f945143f22597baa42557d549a40"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/fastify/fastify-express/security/advisories/GHSA-g6q3-96cp-5r5m"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-177"
        },
        {
          "lang": "en",
          "value": "CWE-288"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.