HTTP Request Smuggler – Burp Plugin to Scan for Smuggling

HTTP Request Smuggler is an extension for Burp Suite designed to help you launch HTTP Request Smuggling attacks, originally created during HTTP Desync Attacks research. It supports scanning for Request Smuggling vulnerabilities, and also aids exploitation by handling cumbersome offset-tweaking for you.

HTTP request smuggling is a technique for interfering with the way a web site processes sequences of HTTP requests that are received from one or more users. Request smuggling vulnerabilities are often critical in nature, allowing an attacker to bypass security controls, gain unauthorized access to sensitive data, and directly compromise other application users.

HTTP Request Smuggler - Burp Extension Smuggling Vulnerabilities
HTTP Request Smuggler – Burp Extension Smuggling Vulnerabilities

HTTP request smuggling vulnerabilities arise in situations where a front-end server forwards multiple requests to a back-end server over the same network connection, and the protocol used for the back-end connections carries the risk that the two servers disagree about the boundaries between requests. Some generic ways to prevent HTTP request smuggling vulnerabilities arising are as follows:

  • Disable reuse of back-end connections, so that each back-end request is sent over a separate network connection.
  • Use HTTP/2 for back-end connections, as this protocol prevents ambiguity about the boundaries between requests.
  • Use exactly the same web server software for the front-end and back-end servers, so that they agree about the boundaries between requests.

In some cases, vulnerabilities can be avoided by making the front-end server normalize ambiguous requests or making the back-end server reject ambiguous requests and close the network connection. However, these approaches are potentially more error-prone than the generic mitigations identified above.

You can read more about this attack and download the extension over here:

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