[28603] in bugtraq
DoS attack on Windows 2000 Terminal Server
daemon@ATHENA.MIT.EDU (Jonathan Hunter)
Thu Jan 23 20:28:22 2003
To: bugtraq@securityfocus.com
From: Jonathan Hunter <jonathan.hunter+dated+1043753340.86cf13@ptel.co.uk>
Date: Thu, 23 Jan 2003 11:29:01 +0000 (GMT)
Message-ID: <1043321341.12794.TMDA@kryten.ninja.org.uk>
This one's short and simple..
Description
-----------
Any user with sufficient permission to log on to a Windows 2000 Terminal
Server (via RDP or ICA) and access its filesystem can reboot the server
at will.
Exploit
-------
- Open %SYSTEMROOT%\SYSTEM32\MSGINA.DLL for exclusive access (read lock).
I used Radsoft's HEXVIEW.EXE from Rix2K to do this.
- Open a new connection to the server via RDP/ICA
- Click the nice, helpful "Restart" button in the warning dialog that
appears ("msgina.dll failed to load")
Tested on Windows 2000 Server (IE55, SP2) and Windows 2000 Server (IE55,
SP3). I do not have easy access to other platforms at the moment.
Workaround
----------
- Remove all permissions from MSGINA.DLL for "Power Users", "Users" and
"Everyone"
Note: The above workaround has been tested on Windows 2000 Server (IE55,
SP2) and users were still able to log in as normal. I am not aware of a
need for MSGINA.DLL to be accessible by normal users, but if there are
any such circumstances Microsoft will need to produce an alternative fix.
Vendor status
-------------
Contacted on 16/01/2003. Replied to my email the next day requesting
additional time to investigate. No further replies since 17/01/2003.
Thanks
------
Thanks to PPH for the use of a Windows 2000 Server IE55,SP2 machine!
