Gadu-Gadu 7.20 allows remote attackers to cause a denial of service via multiple DCC packets with a code of 6 or 7, which triggers a large number of popup windows to the user and creates a large number of threads.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23152
http://www.securityfocus.com/bid/15520/
http://secunia.com/advisories/17597/
http://marc.info/?l=bugtraq&m=113261573023912&w=2
http://archives.neohapsis.com/archives/fulldisclosure/2005-11/0658.html