This indicates an attack attempt to exploit a Memory Corruption vulnerability in LibVNCserver.
The vulnerability is caused by an error when the vulnerable software try to access an object that has already been deleted. A remote attacker can exploit this to execute arbitrary code within context of the affected software.
LibVNCServer Development Team LibVNCServer prior to 0.9.10
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.