ircu 2.10.12.01 allows remote attackers to (1) cause a denial of service (flood wallops) by joining two channels with certain long names that differ in the final character, which triggers a protocol violation and (2) cause a denial of service (daemon crash) via a "J 0:#channel" message on a channel without an apass; and (3) allows remote authenticated operators to cause a denial of service (daemon crash) via a remote "names -D" command.