Sanic's core HTTP/1.1 parser fails to fully consume the `trailer-part` after the terminating zero chunk before reusing the keep-alive connection buffer. A remote unauthenticated client can place attacker-controlled bytes in this trailer region, which Sanic then parses and routes as a hidden second request following the initial outer request. This failure in request-boundary integrity can enable request smuggling when Sanic is deployed behind intermediaries such as reverse proxies, gateways, or caches.