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Microsoft Security Bulletin (MS99-009)
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Patch Available for "Malformed Bind Request" Vulnerability
Originally Posted: March 16, 1999
Summary
=======
Microsoft has released a patch that eliminates a vulnerability in the LDAP
Bind function for Microsoft (r) Exchange (r) 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
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 http://www.microsoft.com/security/services/bulletin.asp for
more information about this free customer service.
Microsoft has published the following Knowledge Base (KB) article on this
issue:
- Microsoft Knowledge Base (KB) article Q221989,
XADM: Buffer Overrun in Exchange 5.5 LDAP Service,
http://support.microsoft.com/support/kb/articles/q221/9/89.asp
(Note: It might take 24 hours from the original posting of
this bulletin for the KB article to be visible in the Web-based
Knowledge Base.)
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:
- X86-based Exchange:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/
fixes/Eng/Exchg5.5/PostSP2/DIR-fix/PSP2DIRI.EXE
- Alpha-based Exchange:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/
fixes/Eng/Exchg5.5/PostSP2/DIR-fix/PSP2DIRA.EXE
(Note: The above URLs have been wrapped for readability)
More Information
================
Please see the following references for more information related to this
issue.
- Microsoft Security Bulletin MS99-009,
Patch Available for "Malformed Bind Request"
Vulnerability (the Web-posted version of this bulletin),
http://www.microsoft.com/security/bulletins/ms99-009.asp.
- Microsoft Knowledge Base (KB) article Q221989,
XADM: Buffer Overrun in Exchange 5.5 LDAP Service.
http://support.microsoft.com/support/kb/articles/q221/9/89.asp
(Note: It might take 24 hours from the original posting of
this bulletin for the KB article to be visible in the Web-based
Knowledge Base.)
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/support/contact/default.asp.
Revisions
=========
- March 16, 1999: Bulletin Created
For additional security-related information about Microsoft
products, please visit http://www.microsoft.com/security
------------------------------------------------------------------------
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(c) 1999 Microsoft Corporation. All rights reserved. Terms of Use.
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