From secnotif@MICROSOFT.COM Fri Dec 17 16:22:38 1999 From: Microsoft Product Security Resent-From: mea culpa To: MICROSOFT_SECURITY@ANNOUNCE.MICROSOFT.COM Resent-To: jericho@attrition.org Date: Thu, 16 Dec 1999 11:47:11 -0800 Subject: Microsoft Security Bulletin (MS99-056) The following is a Security Bulletin from the Microsoft Product Security Notification Service. Please do not reply to this message, as it was sent from an unattended mailbox. ******************************** Microsoft Security Bulletin (MS99-056) -------------------------------------- Patch Available for "Syskey Keystream Reuse" Vulnerability Originally Posted: December 16, 1999 Summary ======= Microsoft has released a patch that eliminates a vulnerability in Syskey, a utility that provides additional protection for Microsoft(r) Windows NT(r) password databases. The vulnerability allows a particular cryptanalytic attack to be effective against Syskey, significantly reducing the strength of the protection it offers. The patch eliminates the vulnerability and restores strong protection to the password database. Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/security/bulletins/MS99-056faq.asp. Issue ===== Syskey is a utility that strongly encrypts the hashed password information in the SAM database in order to protect it against offline password cracking attacks. However, Syskey reuses the keystream used to perform some of the encryption. This significantly reduces the strength of the protection it provides by enabling a well-known cryptanalytic attack to be used against it. A patch is available that eliminates the key reuse vulnerability and again makes it computationally infeasible to mount a brute-force attack against the SAM database when Syskey has been applied. Affected Software Versions ========================== - Microsoft Windows NT Workstation 4.0 - Microsoft Windows NT Server 4.0 - Microsoft Windows NT Server 4.0, Enterprise Edition - Microsoft Windows NT Server 4.0, Terminal Server Edition Patch Availability ================== - x86: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16798 - alpha: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16799 NOTE: Additional security patches are available at the Microsoft Download Center (www.microsoft.com/downloads) More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-056: Frequently Asked Questions, http://www.microsoft.com/security/bulletins/MS99-056faq.asp. - Microsoft Knowledge Base (KB) article Q248183, Syskey Utility Reuses Keystream, http://support.microsoft.com/support/kb/articles/q248/1/83.asp. (Note: It may take 24 hours from the original posting of this bulletin for this KB article to be visible.) - Microsoft Knowledge Base (KB) article Q143475, Windows NT System Key Permits Strong Encryption of the SAM, http://support.microsoft.com/support/kb/articles/q143/4/75.asp. - Microsoft Security Advisor web site, http://www.microsoft.com/security/default.asp. Obtaining Support on this Issue =============================== This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/support/contact/default.asp. Acknowledgments =============== Microsoft acknowledges Bindview's RAZOR Security Team (www.bindview.com) for bringing this issue to our attention. Revisions ========= - December 16, 1999: Bulletin Created. ------------------------------------------------------------------------ THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. 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