[ SOURCE: http://www.secureroot.com/security/advisories/9795498134.html ] -----BEGIN PGP SIGNED MESSAGE----- - ---------------------------------------------------------------------- Title: Web Client NTLM Authentication Vulnerability Date: January 11, 2001 Software: Office 2000, Windows 2000, and Windows Me Impact: NTLM Credentials sent regardless of prompt setting Bulletin: MS01-001 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-001.asp. - ---------------------------------------------------------------------- Issue: ====== The Web Extender Client (WEC) is a component that ships as part of Office 2000, Windows 2000, and Windows Me. WEC allows IE to view and publish files via web folders, similar to viewing and adding files in a directory through Windows Explorer. Due to an implementation flaw, WEC does not respect the IE Security settings regarding when NTLM authentication will be performed - instead, WEC will perform NTLM authentication with any server that requests it. If a user established a session with a malicious user's web site - either by browsing to the site or by opening an HTML mail that initiated a session with it - an application on the site could capture the user's NTLM credentials. The malicious user could then use an offline brute force attack to derive the password or, with specialized tools, could submit a variant of these credentials in an attempt to access protected resources. The vulnerability would only provide the malicious user with the cryptographically protected NTLM authentication credentials of another user. It would not, by itself, allow a malicious user to gain control of another user's computer or to gain access to resources to which that user was authorized access. In order to leverage the NTLM credentials (or a subsequently cracked password), the malicious user would have to be able to remotely logon to the target system. However, best practices dictate that remote logon services be blocked at border devices, and if these practices were followed, they would prevent an attacker from using the credentials to logon to the target system. Mitigating Factors: ==================== - The client would need to be coerced into visiting a malicious web site or read malicious e-mail. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-001.asp for information on obtaining this patch. Acknowledgment: =============== - David Litchfield (http://www.atstake.com) - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. -----BEGIN PGP SIGNATURE----- Version: PGP Personal Privacy 6.5.3 iQEVAwUBOl5RpY0ZSRQxA/UrAQF4oggAhATiZyE/xnueJyvfT1PVGMkjAG8ovrqM uVR0qDLmWMzlAdlSnNynyu6vJyZEHLCklFyM008J8pX6Sk3K+f9DJNLvR/GY8CHX pwjgHpnQuZxxpqBXQXY4bCgDccvqT6+toojYcdpUZT73zXB3TwihALYJccA+Mxxm yrX/3b/WnR8i3V19bpOpL4pCJDEhGHtokHo2W6DNuAQTOS7MNPX8rDvWYu4wHeZx afv++9pMht9mVGDnSeBDVIkAg61KYVRgY8oOKqLp7hjRvAkaDOWj+BdcQxZHttx+ TQ2gSqok2xyRCaKfC3GYugARNf5aJ8QTqLrIl3U319XgzBrIY2yxWg== =/JDx -----END PGP SIGNATURE----- ******************************************************************* You have received this e-mail bulletin as a result of your registration to the Microsoft Product Security Notification Service. You may unsubscribe from this e-mail notification service at any time by sending an e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM The subject line and message body are not used in processing the request, and can be anything you like. To verify the digital signature on this bulletin, please download our PGP key at http://www.microsoft.com/technet/security/notify.asp. For more information on the Microsoft Security Notification Service please visit http://www.microsoft.com/technet/security/notify.asp. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security.