1. Web Security Academy
  2. Request smuggling
  3. Advanced
  4. Request tunnelling
  5. Lab

Lab: Bypassing access controls via HTTP/2 request tunnelling


This lab is vulnerable to request smuggling because the front-end server downgrades HTTP/2 requests and fails to adequately sanitize incoming header names. To solve the lab, access the admin panel at /admin as the administrator user and delete carlos.

The front-end server doesn't reuse the connection to the back-end, so isn't vulnerable to classic request smuggling attacks. However, it is still vulnerable to request tunnelling.


This lab supports HTTP/2 but doesn't advertise this via ALPN. To send HTTP/2 requests using Burp Repeater, you need to enable the Allow HTTP/2 ALPN override option and manually change the protocol to HTTP/2 using the Inspector.

Please note that this feature is only available from Burp Suite Professional / Community 2021.9.1.

Register for free to track your learning progress

The benefits of working through PortSwigger's Web Security Academy
  • Practise exploiting vulnerabilities on realistic targets.

  • Record your progression from Apprentice to Expert.

  • See where you rank in our Hall of Fame.

Already got an account? Login here