Uncontrolled recursion in PostgreSQL SSL and GSS negotiation allows an attacker able to connect to a PostgreSQL AF_UNIX socket to achieve sustained denial of service.  If SSL and GSS are both disabled, an attacker can do the same via access to a PostgreSQL TCP socket.  Versions before PostgreSQL 18.4, 17.10, 16.14, 15.18, and 14.23 are affected.