URL-based access control can be circumvented


This website has an unauthenticated admin panel at /admin, but a front-end system has been configured to block external access to that path. However, the back-end application is built on a framework that supports the X-Original-URL header.

Reproduction and proof of concept

  1. Try to load /admin and observe that you get blocked. The response is very plain, suggesting it may originate from a front-end system.

  2. Send the request to Burp Repeater. Change the URL in the request line to / and add the HTTP header X-Original-URL: /invalid. Observe that the application returns a “not found” response. This indicates that the back-end system is processing the URL from the X-Original-URL header.

  3. Change the value of the X-Original-URL header to /admin. Observe that you can now access the admin page.

  4. To delete the user carlos, add ?username=carlos to the real query string, and change the X-Original-URL path to /admin/delete.



An attacker will need to access the admin panel and delete the user carlos.