Microsoft Windows NT 4.0 RAS Administration Registry Key Vulnerability

[Elias Levy <aleph1 () SECURITYFOCUS COM>]

Title:          Microsoft Windows NT 4.0 RAS Administration Registry Key
                Vulnerability
BID:            2064
Published:      December 06, 2000
Vulnerable:     Microsoft Windows NT 4.0
                Microsoft Windows NT Terminal Server

Description:

The registry key in Windows NT 4.0 that handles the administration of Remote
Access Service (RAS) third-party tools is not properly configured to deny
write access to unprivileged users. Such lenient permissions assigned to this
particular registry key would allow any user that could log on locally to a
system with a RAS server installed to modify the value of the key to an
arbitrary DLL file that would be executed upon startup of RAS. The DLL in the
RAS registry key is run under LocalSystem privileges. Therefore, the malicious
user would be able to perform any action under the LocalSystem security
context which would basically yield full control over the local machine. The
location of the RAS registry key is HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\RAS.

This vulnerability could be exploited remotely if the Winreg key was enabled to allow remote access to the registry 
(Winreg is enabled by default).

RAS is not installed by default on Windows NT 4.0.

Solutions:

Microsoft has released the following tool which corrects the registry key
value (this tool also corrects the registry values for other vulnerabilities
discussed in Microsoft Security Bulletin MS00-095). Please see Frequently
Asked Questions (Microsoft Security Bulletin MS00-095) under "Credit" for
details in regards to proper usage of the tool:

Microsoft patch Q265714i
http://download.microsoft.com/download/winntsp/Patch/Q266794/NT4/EN-US/Q265714i.EXE
Intel

Credit:

Discovered by Milan Dadok and publicized in a Microsoft Security Bulletin
(MS00-095) on December 6, 2000.

Reference:

http://www.securityfocus.com/bid/2064
http://www.microsoft.com/technet/security/bulletin/ms00-095.asp
http://www.microsoft.com/technet/security/bulletin/fq00-095.asp

--
Elias Levy
SecurityFocus.com
http://www.securityfocus.com/
Si vis pacem, para bellum