CVE-2019-16792: Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling)

Waitress allows request smuggling by sending the Content-Length header twice. Waitress would header fold a double Content-Length header and due to being unable to cast the now comma separated value to an integer would set the Content-Length to 0 internally. If two Content-Length headers are sent in a single request, Waitress treats the body of the request as a new request in HTTP pipelining.