Thanks for clarifying.
Today's web applications frequently employ chains of HTTP servers between users and the ultimate application logic. Users send requests to a front-end server (sometimes called a load balancer or reverse proxy) and this server forwards requests to one or more back-end servers. This type of architecture is increasingly common, and in some cases unavoidable, in modern cloud-based applications.
When the front-end server forwards HTTP requests to a back-end server, it typically sends several requests over
the same back-end network connection, because this is much more efficient and performant.
In a request smuggling attack, the attacker (using a
different network connection) causes part of their front-end request to be interpreted by the back-end server as the start of the next request.
Please let us know if you need any further assistance.