Title: XDM Session Cookie Guessing Vulnerability
Severity: HIGH
Description:
xdm is the X Display Manager, a component of the XFree86 package. xdm manages the display of X sessions both locally and remotely.
A problem in xdm makes it possible for a remote users to gain access to the session of another user. This could lead to a remote user gaining access to a local system with the privileges of any user, and potentially as root.
The problem is manifested in X packages that have been compiled with the HasXdmXauth option set. The default compilation of X with this option enabled forces xdm to create it's cookie values using the gettimeofday() call. A remote user that is able to monitor the start of X sessions may use the value from the time the session started in a brute force crack attempt against the server. Knowledge of this value makes a brute force attack trivial.
Affected Products:
- XFree86 X11R6 3.3.0
- XFree86 X11R6 3.3.3
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