Possible RDP vulnerability

[wicked clown <wickedclownuk () googlemail com>]

Hi Guys,



I think I possible may have found a vulnerability with using RDP / Terminal
services on windows 2003.



If you lock down a server and only allow users who connect to your RDP
connection to run certain applications, users can bypass this and run ANY
application they want. You can do this by modifying the RDP profile /
shortcut and add your application to the alternate shell and the shell
working directory.



When the user connects now to the RDP server the banned application will
execute upon logging on even though the user isn’t allowed to execute the
application if the user logs on normally. This doesn’t work with cmd.exe but
I have been able to execute internet explorer, down a modified cmd version,
modify the RDP profile to execute the new cmd and it works like a charm.



I have only been able to tested this on windows 2003 using a local policy
and works like a treat. Even in the wild!



I have done a quick basic video which can been seen here;

http://www.tombstone-bbs.co.uk/v1d30z/rdp-hack2.swf



Instead of modifying the RDP profile, I just added my application to the
program tab.. I know the video is crappy but it’s just meant to give you an
idea what I am talking about :)



So in short, if anybody can access your server via RDP they are NOT
restricted by the policy. I would be interested in any feed back about this
possible exploit / vulnerability even if you don’t think it is.. or even
better if someone knows how to defend againest it!! LOL! :)


Cheers

Wicked Clown.

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