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. Waitress 3.0.1 contains fixes that remove the race condition.
A flaw was found in the Waitress WSGI server for Python. When a remote client closes the connection before waitress has had the opportunity to call `getpeername()`, waitress will incorrectly clean up the connection, leading to the main thread attempting to write to a socket that no longer exists, and that socket is not removed from the list of sockets to attempt to process. This leads to a busy-loop calling the write function. A remote attacker could exhaust the available sockets with very little resources required.
It was discovered that Waitress could process follow up requests when receiving a specially crafted message. An attacker could use this issue to have the server process inconsistent client requests. Dylan Jay discovered that Waitress could be lead to write to an unexisting socket after closing the remote connection. An attacker could use this issue to increase resource utilization leading to a denial of service.
