The IP cloaking feature (cloak.c) in UnrealIRCd 3.2, and possibly other versions, uses a weak hashing scheme to hide IP addresses, which could allow remote attackers to use brute force methods to gain other user's IP addresses.

Format string vulnerability in the Cio_PrintF function of cio_main.c in Unreal IRCd 3.1.1 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via format string specifiers.