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CVE-2026-28289

Estado: AnalizadaAlta (8.1)—

FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207.

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.

Acceso de red sin privilegios (AV:N/PR:N) a aplicación web expuesta; bypass de validación de archivo en FreeScout permite subir .htaccess malicioso para RCE (web shell).

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

Tecnologías afectadas (1)

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-28289",
  "cveTags": [],
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          "options": [
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          "version": "2.0.3",
          "timestamp": "2026-03-04T16:04:55.522646Z"
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      "value": "FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207."
    },
    {
      "lang": "es",
      "value": "FreeScout es una mesa de ayuda gratuita y una bandeja de entrada compartida construida con el framework Laravel de PHP. Una vulnerabilidad de omisión de parche para CVE-2026-27636 en FreeScout 1.8.206 y anteriores permite a cualquier usuario autenticado con permisos de carga de archivos lograr Ejecución Remota de Código (RCE) en el servidor mediante la carga de un archivo .htaccess malicioso utilizando un prefijo de carácter de espacio de ancho cero para omitir la verificación de seguridad. La vulnerabilidad existe en la función sanitizeUploadedFileName() en app/Http/Helper.php. La función contiene una falla de Tiempo de Verificación a Tiempo de Uso (TOCTOU) donde la verificación del prefijo de punto ocurre antes de que la sanitización elimine los caracteres invisibles. Esta vulnerabilidad está corregida en 1.8.207."
    }
  ],
  "lastModified": "2026-06-17T10:28:26.197",
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}