Multiple vulnerabilities in the H.323 protocol implementation for First Virtual Communications Click to Meet Express (when used with H.323 conferencing endpoints), Click to Meet Premier, Conference Server, and V-Gate allow remote attackers to cause a denial of service, as demonstrated by the NISCC/OUSPG PROTOS test suite for the H.225 protocol.
http://www.uniras.gov.uk/vuls/2004/006489/h323.htm
http://www.cert.org/advisories/CA-2004-01.html
http://support.fvc.com/eng/docs/misc_docs/H.323_Security_Bulletin.pdf