Multiple buffer overflows in Gaim 0.75 and earlier and Ultramagnetic before 0.81 allow remote attackers to cause a denial of service and possibly execute arbitrary code via (1) cookies in a Yahoo web connection (2) a long name parameter in the Yahoo login web page (3) a long value parameter in the Yahoo login page (4) a YMSG packet (5) the URL parser and (6) HTTP proxy connect.