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.
https://exchange.xforce.ibmcloud.com/vulnerabilities/8360
http://www.securiteam.com/unixfocus/5MP080A6LQ.html
http://archives.neohapsis.com/archives/vuln-dev/2002-q1/0664.html