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securityvulnsSecurityvulnsSECURITYVULNS:DOC:4017
HistoryJan 24, 2003 - 12:00 a.m.

DoS attack on Windows 2000 Terminal Server

2003-01-2400:00:00
vulners.com
8

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!