Buffer overflows in Yahoo! Messenger 5,0,0,1064 and earlier allows remote attackers to execute arbitrary code via a ymsgr URI with long arguments to (1) call, (2) sendim, (3) getimv, (4) chat, (5) addview, or (6) addfriend.
http://www.securityfocus.com/bid/4837
http://www.kb.cert.org/vuls/id/137115