The CtcpParser::packedReply method in core/ctcpparser.cpp in Quassel before 0.7.3 allows remote attackers to cause a denial of service (crash) via a crafted Client-To-Client Protocol (CTCP) request, as demonstrated in the wild in September 2011.

Quassel before 0.12-rc1 uses an incorrect data-type size when splitting a message, which allows remote attackers to cause a denial of service (crash) via a long CTCP query containing only multibyte characters.

Stack consumption vulnerability in the message splitting functionality in Quassel before 0.12-rc1 allows remote attackers to cause a denial of service (uncontrolled recursion) via a crafted massage.

Quassel before 0.12.2 does not properly re-initialize the database session when the PostgreSQL database is restarted, which allows remote attackers to conduct SQL injection attacks via a \ (backslash) in a message. NOTE: this vulnerability exists because of an incomplete fix for CVE-2013-4422.

The CoreUserInputHandler::doMode function in core/coreuserinputhandler.cpp in Quassel 0.10.0 allows remote attackers to cause a denial of service (application crash) via the "/op *" command in a query.

The onReadyRead function in core/coreauthhandler.cpp in Quassel before 0.12.4 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via invalid handshake data.