24th Jan 2003 [SBWID-5949]
COMMAND
Windows 2000 Terminal Server DoS attack
SYSTEMS AFFECTED
Windows 2000 Terminal Server
PROBLEM
Jonathan Hunter says :
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).
SOLUTION
no patch yet.
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.