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Title: Cumulative Patch for Internet Explorer (822925)
Date: 20 August 2003
- Microsoft Internet Explorer 5.01
- Microsoft Internet Explorer 5.5
- Microsoft Internet Explorer 6.0
- Microsoft Internet Explorer 6.0 for Windows Server 2003
Impact: Run code of the attacker's choice
Max Risk: Critical
Microsoft encourages customers to review the Security Bulletins
This is a cumulative patch that includes the functionality of all
previously released patches for Internet Explorer 5.01, 5.5 and
6.0. In addition, it eliminates the following newly discovered
- A vulnerability involving the cross-domain security model of
Internet Explorer, which keeps windows of different domains from
sharing information. This flaw could result in the execution of
script in the My Computer zone. To exploit this flaw, an attacker
would have to host a malicious Web site that contained a Web page
designed to exploit this particular vulnerability and then
persuade a user to visit that site. After the user has visited
the malicious Web site, it would be possible for the attacker to
run malicious script by misusing the method Internet Explorer
uses to retrieve files from the browser cache, and cause that
script to access information in a different domain. In the worst
case, this could enable the Web site operator to load malicious
script code onto a user's system in the security context of the
My Computer zone. In addition, this flaw could also enable an
attacker to run an executable file that was already present on
the local system or view files on the computer. The flaw exists
because a file from the Internet or intranet with a maliciously
constructed URL can appear in the browser cache running in the My
- A vulnerability that occurs because Internet Explorer does not
properly determine an object type returned from a Web server. It
could be possible for an attacker who exploited this
vulnerability to run arbitrary code on a user's system. If a user
visited an attacker's Web site, it would be possible for the
attacker to exploit this vulnerability without any other user
action. An attacker could also craft an HTML-based e-mail that
would attempt to exploit this vulnerability.
This patch also sets the Kill Bit on the BR549.DLL ActiveX
control. This control implemented support for the Windows
Reporting Tool, which is no longer supported by Internet
Explorer. The control has been found to contain a security
vulnerability. To protect customers who have this control
installed, the patch prevents the control from running or from
being reintroduced onto users' systems by setting the Kill Bit
for this control. This issue is discussed further in Microsoft
Knowledge Base article 822925.
In addition to these vulnerabilities, a change has been made to
the way Internet Explorer renders HTML files. This change
addresses a flaw in the way Internet Explorer renders Web pages
that could cause the browser or Outlook Express to fail. Internet
Explorer does not properly render an input type tag. A user
visiting an attacker's Web site could allow the attacker to
exploit the vulnerability by viewing the site. In addition, an
attacker could craft a specially formed HTML-based e-mail that
could cause Outlook Express to fail when the e-mail was opened or
This patch also contains a modification to the fix for the Object
Type vulnerability (CAN-2003-0344) corrected in Microsoft
Security Bulletin MS03-020. The modification corrects the
behavior of the fix to prevent the attack on specific languages.
To exploit these flaws, the attacker would have to create a
specially formed HTML-based e-mail and send it to the user.
Alternatively an attacker would have to host a malicious Web site
that contained a Web page designed to exploit these
vulnerabilities. The attacker would then have to persuade a user
to visit that site.
As with the previous Internet Explorer cumulative patches
released with bulletins MS03-004, MS03-015, and MS03-020 this
cumulative patch will cause window.showHelp( ) to cease to
function if you have not applied the HTML Help update. If you
have installed the updated HTML Help control from Knowledge Base
article 811630, you will still be able to use HTML Help
functionality after applying this patch.
- By default, Internet Explorer on Windows Server 2003 runs in
Enhanced Security Configuration. This default configuration of
Internet Explorer blocks these attacks. If Internet Explorer
Enhanced Security Configuration has been disabled, the
protections put in place that prevent these vulnerabilities from
being exploited would be removed.
- In the Web-based attack scenario, the attacker would have to
host a Web site that contained a Web page used to exploit these
vulnerabilities. An attacker would have no way to force users to
visit a malicious Web site outside the HTML-based e-mail vector.
Instead, the attacker would need to lure them there, typically by
getting them to click a link that would take them to the
- Code that executed on the system would only run under the
privileges of the logged-on user.
- A patch is available to fix this vulnerability. Please read
the Security Bulletins at:
for information on obtaining this patch.
- Microsoft thanks the following for working with us to protect
- Yu-Arai of LAC for reporting the language specific variant of
the MS03-020 Object Type vulnerability (CAN-2003-0344), as well
as the Browser Cache Script Execution in My Computer Zone problem
- eEye Digital Security for reporting the Object Type
vulnerability to us.
- Greg Jones from KPMG UK for reporting the BR549.DLL Buffer
Overrun problem to us.
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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