Buffer overflow in Yahoo! Messenger 5.0 allows remote attackers to cause a denial of service and possibly execute arbitrary code via a long (1) message or (2) IMvironment field.
http://www.securityfocus.com/bid/4163
http://www.securityfocus.com/bid/4162
http://www.kb.cert.org/vuls/id/887319
http://www.kb.cert.org/vuls/id/419419
http://www.iss.net/security_center/static/8265.php
http://www.iss.net/security_center/static/8264.php