Updated VNC packages are available to fix a challenge replay attack that is present in the VNC server.
VNC is a tool for providing a remote graphical user interface. The VNC DES authentication scheme is implemented using a challenge-response architecture, producing a random and different challenge for each authentication attempt. A bug in the function for generating the random challenge caused the random seed to be reset to the current time on every authentication attempt. As a result, two authentication attempts within the same second could receive the same challenge. An eavesdropper could exploit this vulnerability by replaying the response, thereby gaining authentication. All users of VNC are advised to upgrade to these errata packages, which contain an updated version and are not vulnerable to this issue. Note that when using VNC on an untrusted network, always make sure to tunnel the VNC protocol through a secure, authenticated channel such as SSH. Instructions on how to tunnel VNC through SSH are provided at the following URL: http://www.uk.research.att.com/vnc/sshvnc.html