Bird Chat 1.61 allows remote attackers to cause a denial of service (crash) via invalid users.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17080
https://euvd.enisa.europa.eu/vulnerability/EUVD-2004-1733
http://www.securityfocus.com/bid/11010
http://www.autistici.org/fdonato/advisory/BirdChat1.61-adv.txt