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Microsoft Security Bulletin MS99-020 - Important

Patch Available for "Malformed LSA Request" Vulnerability

Published: June 23, 1999 | Updated: March 21, 2003

Version: 2.0

Patch Availability Information Updated: March 21, 2003
Originally Posted: June 23, 1999
Revised: July 20, 1999

Summary

Microsoft has released a patch that eliminates a vulnerability that poses a denial of service threat to Microsoft® Windows NT® servers and workstations. A malformed request to the Local Security Authority (LSA) service will causes the service to stop responding, requiring the computer to be restarted.

A fully supported patch is available to eliminate the vulnerability, and Microsoft recommends that affected customers download and install it, if appropriate.

Issue

Windows NT provides the ability to manage user privileges programmatically via the Local Security Authority (LSA) API. The API allows a program to query user names, modify privileges, and change other elements of the security policy, subject to the program's authorizations. Calls to the LSA API can be made from either the local machine or remotely via RPC.

Certain API methods do not correctly handle certain types of invalid arguments. The vulnerability is a denial of service threat only, and service can be restored by restarting the machine. There is no capability to use this vulnerability to obtain unauthorized services from LSA.

While there are no reports of customers being adversely affected by this vulnerability, Microsoft is proactively releasing this patch to allow customers to take appropriate action to protect themselves against it.

Affected Software Versions

  • Microsoft Windows NT 4.0 Workstation
  • Microsoft Windows NT 4.0 Server
  • Microsoft Windows NT 4.0 Server, Terminal Server Edition, 4.0

Vulnerability Identifier: CVE-1999-0721

What Microsoft is Doing

Microsoft has released patches that fix the problem identified. The patches are available for download from the sites listed below in What Customers Should Do.

Microsoft also has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See The Microsoft Product Security Notification Service for more information about this free customer service.

Microsoft has published the following Knowledge Base (KB) article on this issue:

What Customers Should Do

Microsoft has released patches that fix the problem identified. Microsoft highly recommends that customers evaluate the degree of risk that this vulnerability poses to their systems and determine whether to download and install the patch. The patch can be found at: http://www.microsoft.com/technet/security/patchavailability.mspx

More Information

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

Obtaining Support on this Issue

If you require technical assistance with this issue, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/contactussupport/?ws=support.

Acknowledgments

Microsoft acknowledges BindView Corporation (http://www.bindview.com) for discovering the vulnerability and reporting it to us.

Revisions

  • June 23, 1999: Bulletin Created.
  • July 20, 1999: Revised.
  • V2.0 (March 21, 2003): Introduced versioning and updated patch availability information

For additional security-related information about Microsoft products, please visit http://www.microsoft.com/technet/security

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