This indicates an attack attempt to exploit a Buffer Overflow Vulnerability in UltraVNC Project UltraVNC
A remote attacker can exploit this vulnerability by sending malicious packets to an UltraVNC server. Successful exploitation could result in denial of service conditions on the target server.
UltraVNC Project UltraVNC prior to revision 1212
UltraVNC Project UltraVNC 184.108.40.206 and earlier
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.