Ubuntu Security Notice 991-1 – Jima discovered that quassel would respond to a single privmsg containing multiple CTCP requests with multiple NOTICEs, possibly resulting in a denial of service against the IRC connection.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/94202/USN-991-1.txt
Source: https://packetstormsecurity.com/files/94202/Ubuntu-Security-Notice-991-1.html