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CVE-2026-21868

Estado: AnalizadaAlta (7.5)—

Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path.

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 ReDoS en API expuesta sin autenticación (PR:N) accesible por red (AV:N). El ataque causa DoS de aplicación consumiendo recursos CPU del servidor MongoDB.

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

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Flagforge — Flagforge

CWE

Referencias

JSON original (NVD)

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      "value": "Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expression dynamically using unescaped user input (the username parameter). An attacker can exploit this by sending a specially crafted username containing regex meta-characters (e.g., deeply nested groups or quantifiers), causing the MongoDB regex engine to consume excessive CPU resources. This can lead to Denial of Service for other users. The issue is fixed in version 2.3.3. To workaround this issue, implement a Web Application Firewall (WAF) rule to block requests containing regex meta-characters in the URL path."
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      "lang": "es",
      "value": "Flag Forge es una plataforma de Capture The Flag (CTF). Las versiones 2.3.2 e inferiores tienen una vulnerabilidad de denegación de servicio por expresión regular (ReDoS) en el endpoint de la API de perfil de usuario (/api/user/[username]). La aplicación construye una expresión regular dinámicamente utilizando entrada de usuario sin escapar (el parámetro username). Un atacante puede explotar esto enviando un nombre de usuario especialmente diseñado que contenga metacaracteres de regex (p. ej., grupos anidados profundamente o cuantificadores), lo que provoca que el motor de regex de MongoDB consuma recursos excesivos de CPU. Esto puede llevar a la denegación de servicio para otros usuarios. El problema está solucionado en la versión 2.3.3. Como solución alternativa a este problema, implemente una regla de cortafuegos de aplicaciones web (WAF) para bloquear las solicitudes que contengan metacaracteres de regex en la ruta URL."
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  "lastModified": "2026-06-17T10:19:03.550",
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