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Microsoft Web Client Extender NTLM Authentication Vulnerability

Web Extender Client (WEC) is a feature in Office 2000, Windows 2000 and Windows ME used in web publishing. WEC enables a user to manipulate basic file functions such as DIR using the HTTP protocol.

Due to a design error, WEC does not implement the security zone settings in Internet Explorer. The vulnerability lies within the fact that WEC may initiate a NTLM challenge-response session with any server even if it is not trusted. Therefore, a malicious user could possibly obtain third-party NTLM credentials by either creating a HTML or email message which requests a session that would automatically send NTLM credentials back to the malicious user. They could then apply brute force techniques to the recovered data to access a valid password.

Successful exploitation of this vulnerability could lead to the disclosure of sensitive information and possibly assist in further attacks against the victim.