From secnotif@MICROSOFT.COM Mon Oct 25 11:44:27 1999 From: Microsoft Product Security Resent-From: mea culpa To: MICROSOFT_SECURITY@ANNOUNCE.MICROSOFT.COM Resent-To: jericho@attrition.org Date: Fri, 22 Oct 1999 18:03:11 -0700 Subject: Microsoft Security Bulletin (MS99-046) 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 (MS99-046) -------------------------------------- Patch Available to Improve TCP Initial Sequence Number Randomness Originally Posted: October 22, 1999 Summary ======= Microsoft has released a patch that significantly improves the randomness of the TCP initial sequence numbers (ISNs) generated by the TCP/IP stack in Microsoft(r) Windows NT(r) 4.0. Improving the randomness of ISNs eliminates a class of potential attacks against Windows NT 4.0 systems. Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/security/bulletins/MS99-046faq.asp. Issue ===== The ISNs used in TCP/IP sessions should be as random as possible in order to prevent attacks such as IP address spoofing and session hijacking. This patch improves the randomness of the Windows NT 4.0 TCP/IP ISN generation, providing 15 bits of entropy. Affected Software Versions ========================== - Microsoft Windows NT 4.0 Workstation - Microsoft Windows NT 4.0 Server - Microsoft Windows NT 4.0 Server, Enterprise Edition - Microsoft Windows NT 4.0 Server, Terminal Server Edition Patch Availability ================== - x86: http://download.microsoft.com/download/winntsrv40/patch/ 4.0.1381.7014/nt4/en-us/q243835.exe - Alpha: http://download.microsoft.com/download/winntsrv40/patch/ 4.0.1381.7014/alpha/en-us/q243835.exe NOTE: Line breaks have been inserted into the above URLs for readability. More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-046: Frequently Asked Questions, http://www.microsoft.com/security/bulletins/MS99-046faq.asp. - Microsoft Knowledge Base (KB) article Q243835, How to Prevent Predictable TCP/IP Initial Sequence Numbers, http://support.microsoft.com/support/kb/articles/q243/8/35.asp. (Note: It may take 24 hours from the original posting of this bulletin for this KB article to be visible.) - CERT Advisory CA-95.01, Topic: IP Spoofing Attacks and Hijacked Terminal Connections, http://www.cert.org/advisories/ CA-95.01.IP.spoofing.attacks.and.hijacked.terminal.connections.html. (Note: A line break has been inserted into the above URL for readability) - 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 National Bank of Kuwait for bringing this issue to our attention. Revisions ========= - October 22, 1999: Bulletin Created. ----------------------------------------------------------------------- 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. (c) 1999 Microsoft Corporation. All rights reserved. Terms of Use. ******************************************************************* 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. For more information on the Microsoft Security Notification Service please visit http://www.microsoft.com/security/services/bulletin.asp. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security.