Family: Red Hat Local Security Checks --> Category: infos
RHSA-2002-287: vnc Vulnerability Scan
Vulnerability Scan Summary
Check for the version of the vnc packages
Detailed Explanation for this Vulnerability Test
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
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
Solution : http://rhn.redhat.com/errata/RHSA-2002-287.html
Threat Level: High
Click HERE for more information and discussions on this network vulnerability scan.