HTTP Request Smuggling

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.

Tooling

HTTP Request Smuggler

References

What is HTTP request smuggling? Tutorial & Examples | Web Security AcademyWebSecAcademy