Integer signing errors were found in TightVNC. By exploiting this vulnerability malicious users can cause denial of service or possibly execute arbitrary code. This vulnerability can be exploited remotely via a specially designed message.

UltraVNC 1.0.2
UltraVNC 1.0.5
TightVnc 1.3.9

Update to latest version
TightVNC

The following public exploits exists for this vulnerability:

https://www.exploit-db.com/exploits/8024

https://www.exploit-db.com/exploits/7990