Missing Release of Resource after Effective Lifetime in waitress

Summary

Waitress is a Web Server Gateway Interface server for Python 2 and 3. When a remote client closes the connection before waitress has had the opportunity to call "getpeername()" waitress won't correctly clean up the connection, leading to the main thread attempting to write to a socket that no longer exists, but not removing it from the list of sockets to attempt to process. This leads to a busy-loop calling the "write" function. A remote attacker could run waitress out of available sockets with very little resources required. This vulnerability affects waitress package versions prior to 3.0.1.