Software Engineering Institute

UltraVNC viewer is a remote desktop application that allows a user to control compatible VNC servers. The UltraVNC viewer includes a listen mode that accepts connections from remote hosts.

The UltraVNC viewer contains a buffer overflow vulnerability. This vulnerability may be triggered by sending a malformed packet during the protocol negotiation phase of a VNC session.

A remote, unauthenticated attacker may be able to execute arbitrary code.

Upgrade
See the UltraVNC download page for information about obtaining fixed software.

Data Stream Encryption Plugin

Using the Data Stream Encryption (DSM) plugin will prevent this vulnerability from being exploited by attackers who do not have access to the encryption key material.

Restrict access

Restricting access to a vulnerable system by using host or network based firewalls may prevent a remote attacker from exploiting this vulnerability. Microsoft Windows XP users should see the Technet article How to Configure Windows Firewall on a Single Computer and Windows Vista and Server 2008 users should refer to the Vista Technet article Getting Started with Windows Firewall with Advanced Security in Windows Vista and Windows Server 2008 for more information about configuring the Windows Firewall. Note that UltraVNC runs on ports 5500/tcp and 5400/tcp by default.