ircu 2.10.12.02 through 2.10.12.04 allows remote attackers to cause a denial of service (memory and bandwidth consumption) by creating a large number of unused channels (zannels).
ircu 2.10.12.01 through 2.10.12.04 does not remove ops privilege after a join from a server with an older timestamp (TS), which allows remote attackers to gain control of a channel during a split.
ircu 2.10.12.03 and 2.10.12.04 does not associate a timestamp with ops privilege on an unused channel (zannel), which allows remote attackers to (1) set or remove certain channel modes via a "netriding" attack or (2) take over a channel by joining an unlinked server with the A/Upass and then setting a new Apass.
Race condition in ircu 2.10.12.01 through 2.10.12.05 allows remote attackers to set a new Apass during a netburst by arranging for ops privilege to be granted before the mode arrives.