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Microsoft Security Bulletin MS99-009 - Critical

Patch Available for "Malformed Bind Request" Vulnerability

Published: March 16, 1999 | Updated: March 10, 2003

Version: 2.0

Patch Availability Information Updated: March 10, 2003
Originally Posted: March 16, 1999

Summary

Microsoft has released a patch that eliminates a vulnerability in the LDAP Bind function for Exchange 5.5. The vulnerability could allow denial of service attacks against an Exchange server or, under certain conditions, could allow arbitrary code to be run on the server.

A fully supported patch is available, and Microsoft recommends that customers who are at risk from this attack download and install it.

Issue

The Bind function in the Exchange 5.5 Directory Service has an unchecked buffer that poses two threats to safe operation. The first is a denial of service threat. A malformed Bind request could overflow the buffer, causing the Exchange Directory service to crash. The server would not need to be rebooted, but the Exchange Directory service, and possibly dependent services as well, would need to be restarted in order to resume messaging service. The second threat is more esoteric and would be far more difficult to exploit. A carefully-constructed Bind request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither attack could occur accidentally.

Customers who are using Exchange but who have turned off LDAP support in the Directory Service are not at risk from this vulnerability. Customers also can reduce their vulnerability to attacks from external sources by filtering incoming packets destined for TCP port 389, the LDAP service port.

Microsoft has no reports of any customers being affected by this vulnerability. However, Microsoft is proactively releasing a patch that corrects the problem.

Affected Software Versions

  • Microsoft Exchange Server 5.5

Vulnerability Identifier: CVE-1999-0385

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 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:

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 ISS' X-Force for discovering this vulnerability and working with us to develop a patch.

Revisions

  • March 16, 1999: Bulletin Created
  • V2.0 (March 10, 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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