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Microsoft Security Bulletin MS99-046 - Critical

Patch Available to Improve TCP Initial Sequence Number Randomness

Published: October 22, 1999 | Updated: December 23, 1999

Version: 1.2

Originally Posted: October 22, 1999
Updated: December 23, 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® Windows NT® 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/technet/security/bulletin/fq99-046.mspx.

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

Vulnerability Identifier: CVE-2000-0328

Patch Availability

Windows NT 4.0 Workstation, Windows NT 4.0 Server, and Windows NT 4.0 Server, Enterprise Edition:

More Information

Please see the following references for more information related to this issue.

Obtaining Support on this Issue

This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/contactussupport/?ws=support.

Acknowledgments

Microsoft acknowledges National Bank of Kuwait for bringing this issue to our attention.

Revisions

  • October 22, 1999: Bulletin Created.
  • November 12, 1999: Bulletin changed to announce temporary unavailability of patch.
  • December 23, 1999: Bulletin changed to announce reavailability of patch.

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