Buffer overflow in client for Half-Life 1.1.0.8 and earlier allows malicious remote servers to execute arbitrary code via a long console command.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7148
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0946
http://archives.neohapsis.com/archives/bugtraq/2001-09/0178.html