SecurityFocus.com: XFree86 Xserver Denial of Service Vulnerability

“A denial of service exists in XFree86 3.3.5, 3.3.6 and 4.0.
A remote user can send a malformed packet to the TCP listening
port, 6000, which will cause the X server to be unresponsive for
some period of time. During this time, the keyboard will not
respond to user input, and in some cases, the mouse will also not
respond. During this time period, the X server will utilize 100% of
the CPU, and can only be repaired by being signaled. This
vulnerability exists only in servers compiled with the XCSECURITY
#define set. This can be verified by running the following:
strings /path/to/XF86_SVGA | grep “XC-QUERY-SECURITY-1” “

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