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 blowfishECB function in core/cipher.cpp in Quassel IRC 0.10.0 allows remote attackers to cause a denial of service (out-of-bounds read) via a malformed string.