Buffer overflow in the getnickuserhost function in BNC 2.8.9, and possibly other versions, allows remote IRC servers to execute arbitrary code via an IRC server response that contains many (1) ! (exclamation) or (2) @ (at sign) characters.
https://exchange.xforce.ibmcloud.com/vulnerabilities/18013
http://www.securityfocus.com/bid/11647
http://www.debian.org/security/2004/dsa-595
http://security.lss.hr/en/index.php?page=details&ID=LSS-2004-11-03