The aaugustin websockets library before 9.1 for Python has an Observable Timing Discrepancy on servers when HTTP Basic Authentication is enabled with basic_auth_protocol_factory(credentials=…). An attacker may be able to guess a password via a timing attack.
The Python websockets library version 4 contains a CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in Servers and clients, unless configured with compression=None that can result in Denial of Service by memory exhaustion. This attack appears to be exploitable via sending a specially crafted frame on an established connection. This vulnerability appears to have been fixed in version 5.0