rustls-mio/examples/tlsserver.rs in the rustls crate before 0.16.0 for Rust allows attackers to cause a denial of service (loop of conn_event and ready) by arranging for a client to never be writable.
Rustls is a modern TLS library written in Rust. `rustls::ConnectionCommon::complete_io` could fall into an infinite loop based on network input. When using a blocking rustls server, if a client send a `close_notify` message immediately after `client_hello`, the server's `complete_io` will get in an infinite loop. This vulnerability is fixed in 0.23.5, 0.22.4, and 0.21.11.