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===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2001.236 -- Microsoft Security Bulletin MS01-030 (version 3.0)
Incorrect Attachment Handling in Exchange OWA Can Execute Script
15 June 2001
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Exchange 5.5
Exchange 2000
Vendor: Microsoft
Operating System: Windows
Impact: Execute Arbitrary Code/Commands
Access Privileged Data
Access Required: Remote
Ref: ESB-2001.230
ESB-2001.227
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Title: Incorrect Attachment Handling in Exchange OWA Can
Execute Script
Date: 06 June 2001
Revised: 13 June 2001 (version 3.0)
Software: Exchange 5.5, Exchange 2000
Impact: Run code of attacker's choice on mail client
Bulletin: MS01-030
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-030.asp.
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Reason for Revision:
====================
On June 12, 2001 Microsoft discovered that the updated Exchange 2000
patch contained outdated files. We have corrected the error and
provided an updated version of this patch for Exchange 2000. We
recommend that all customers who have downloaded the Exchange 2000
patch prior to June 12, 2001 install the updated version.
Issue:
======
OWA is a service of Exchange Server that allows users to use a web
browser to access their Exchange mailbox. However, a flaw exists in
the
interaction between OWA and IE for message attachments. If an
attachment contains HTML code including script, the script will be
executed when the attachment is opened, regardless of the attachment
type. Because OWA requires that scripting be enabled in the zone
where
the OWA server is located, this script could take action against the
user's Exchange mailbox.
An attacker could use this flaw to construct an attachment containing
malicious script code. The attacker could then send the attachment in
a
message to the user. If the user opened the attachment in OWA, the
script would execute and could take action against the user's mailbox
as if it were the user, including, under certain circumstances,
manipulation of messages or folders.
Mitigating Factors:
====================
- - - The vulnerability could only be exploited if the user were
using OWA in conjunction with IE.
- The vulnerability is only exploitable by attachments that
are received via OWA. In general, an attacker would have no
way to determine whether a user would open an attachment
using OWA rather than an Outlook client.
- An attacker's ability to exploit this vulnerability would
require that she entice the user to open an attachment from
an untrusted source. Best practices recommend against opening
any attachment from an unknown or untrusted source.
Patch Availability:
===================
- - - A patch is available to fix this vulnerability. Please read the
Security Bulletin
http://www.microsoft.com/technet/security/bulletin/ms01-030.asp
for information on obtaining this patch.
Acknowledgment:
===============
- - - Joao Gouveia (tharbad@kaotik.org)
- - ---------------------------------------------------------------------
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.
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