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 execution of arbitrary code under the security context of the UltraVNC service on the target server.
UltraVNC Project UltraVNC prior to revision 1212
UltraVNC Project UltraVNC 184.108.40.206 and earlier
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.