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.