This indicates an attack attempt to exploit a Denial of Service vulnerability in LibVNCserver.
The vulnerability is caused by an error when the vulnerable software handles a malicious packet. It allows a remote attacker to cause denial of service conditions in the affected application.
LibVNCServer Development Team LibVNCServer 0.9.9 and prior
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.