GHSA-6HR6-W5QG-QMWG h2: Duplicate Host header could facilitate request smuggling

Impact h2 =4.4.0 accepts request header blocks containing more than one Host header, and forwards every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, which is a request smuggling primitive CWE-444...