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Q307195: XWEB: Unauthenticated User Can Enumerate Global Address List

Article: Q307195
Product(s): Microsoft Exchange
Version(s): 5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4
Operating System(s): 
Keyword(s): kbSecurity kbExchange550preSP5fix KbSECVulnerability KbSECHack
Last Modified: 08-MAY-2002

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The information in this article applies to:

- Microsoft Exchange Server, versions 5.5, 5.5 SP1, 5.5 SP2, 5.5 SP3, 5.5 SP4 
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SYMPTOMS
========

An information disclosure vulnerability exists in Exchange Server 5.5 that an
Internet-based attacker can use to learn the e-mail addresses of users on a
corporate Exchange Server 5.5 computer if the server is configured to offer
Microsoft Outlook Web Access (OWA).

The vulnerability does not allow the attacker to read, write, or change any of
the users' e-mail, or to take any other action against the users. The
vulnerability also does not allow the attacker to gain any privileges on the
server. The vulnerability's sole effect is to allow the attacker to learn the
e-mail names of users on the server. This vulnerability does not affect
Microsoft Exchange 2000 Server.

CAUSE
=====

This problem can occur because a function in OWA that queries the Global Address
List does not require authentication. Unauthenticated users can call the
function and enumerate the mail addresses of users on the server.

RESOLUTION
==========

A supported fix is now available from Microsoft, but it is only intended to
correct the problem described in this article and should be applied only to
systems that are determined to be at risk of attack. Please evaluate your
computer's physical accessibility, network and Internet connectivity, and other
factors to determine the degree of risk to your computer. Please see the
associated Microsoft Security Bulletin
(http://www.microsoft.com/technet/security/bulletin/MS01-047.asp) to help make
this determination. This fix may receive additional testing at a later time, to
further ensure product quality. If your computer is sufficiently at risk,
Microsoft recommends that you apply this fix now. Otherwise, wait for the next
Microsoft Exchange Server 5.5 service pack that contains this fix.

To resolve this problem immediately, download the fix as instructed below or
contact Microsoft Product Support Services to obtain the fix. For a complete
list of Microsoft Product Support Services phone numbers and information on
support costs, please go to the following address on the World Wide Web:

  http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are normally incurred for support calls may
be canceled, if a Microsoft Support Professional determines that a specific
update will resolve your problem. Normal support costs will apply to additional
support questions and issues that do not qualify for the specific update in
question.

The following file is available for download from the Microsoft Download Center:

  DownloadDownload Q307195engi386.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=32483)

  NOTE: This patch can be applied to any language version.

Release Date: September 6, 2001

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. After it is posted, the file is housed on
secure servers that prevent any unauthorized changes to the file.

The English version of this fix should have the following file attributes or
later:

Component: OWA

+---------------------+
| File name | Version | 
+---------------------+
| Fumsg.asp | NA      | 
+---------------------+

NOTE: Because of file dependencies, this fix requires Microsoft Exchange Server
version 5.5 Service Pack 4.



STATUS
======

Microsoft has confirmed that this problem could result in some degree of
security vulnerability in Microsoft Exchange Server version 5.5.

MORE INFORMATION
================

For more information on this vulnerability, see the following Microsoft Web
site:

  http://www.microsoft.com/technet/security/bulletin/MS01-047.asp

Additional query words: security_patch GAL

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Keywords          : kbSecurity kbExchange550preSP5fix KbSECVulnerability KbSECHack 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2 kbExchange550SP1 kbExchange550SP2 kbExchange550SP3 kbExchange550SP4
Version           : :5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4
Issue type        : kbbug
Solution Type     : kbfix

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