Vulnerability Note VU#721460

UltraVNC buffer overflow vulnerability

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.

II. Impact

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.

Systems Affected

http://forum.ultravnc.info/viewtopic.php?t=11850
http://forum.ultravnc.info/viewtopic.php?p=43529
http://secunia.com/advisories/28747/
http://www.microsoft.com/technet/security/smallbusiness/prodtech/windowsxp/cfgfwall.mspx
http://technet2.microsoft.com/WindowsVista/en/library/19b429b3-c32b-4cbd-ae2a-8e77f2ced35c1033.mspx?mfr=true
http://forum.ultravnc.info/viewtopic.php?t=6005&highlight=5400

Credit

Thanks to the UltraVNC team and Secunia for information that was used in this report.

This document was written by Ryan Giobbi.

Other Information

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