Vulnérabilités critiques ds IE 5.01, 5.5 et 6

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          S E C U S E R   A L E R T  21/08/03
                http://www.secuser.com/
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             Vulnérabilités critiques dans
          Internet Explorer 5.01, 5.5 et 6.0
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1. RESUME DE L'ALERTE
2. LOGICIEL(S) AFFECTE(S)
3. CORRECTIF DISPONIBLE
4. AIDE ET DISCUSSION
5. FAIRE CONNAITRE SECUSER ALERT
6. CONTACTER SECUSER.COM
7. DESABONNEMENT ET CHANGEMENT D'ADRESSE


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1. RESUME DE L'ALERTE
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Un nouveau correctif cumulatif est disponible pour les navigateurs Internet
Explorer 5.01, 5.5 et 6.0. En plus de toutes les vulnérabilités connues, ce
patch corrige notamment deux nouvelles failles qui permettent à une personne
malveillante ou à un virus d'exécuter le code de son choix sur l'ordinateur
de sa victime, via une page web ou un message piégé au format HTML.
http://www.secuser.com/communiques/2003/030821_patchie.htm

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2. LOGICIEL(S) AFFECTE(S)
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Internet Explorer 5.01
Internet Explorer 5.5
Internet Explorer 6.0

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3. CORRECTIF DISPONIBLE
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Les utilisateurs concernés doivent appliquer dès que possible le correctif
correspondant à la version de leur logiciel par l'intermédiaire du service
WindowsUpdate ou en téléchargeant le correctif sur le site de l'éditeur.
http://www.secuser.com/outils/index.htm#windowsupdate
http://www.secuser.com/communiques/2003/030821_patchie.htm#correctif

=====================================================================
                                 CERT-Renater


                      Note d'Information No. 2003/VULN271
_____________________________________________________________________


DATE                      : 21/08/2003


HARDWARE PLATFORM(S)      : /


OPERATING SYSTEM(S)       : Systems running Internet Explorer
                            
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Title:      Cumulative Patch for Internet Explorer (822925)
Date:       20 August 2003
Software:  


 - 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
Bulletin:   MS03-032


Microsoft encourages customers to review the Security Bulletins
at:
http://www.microsoft.com/technet/security/bulletin/MS03-032.asp
http://www.microsoft.com/security/security_bulletins/ms03-032.asp
- -----------------------------------------------------------------


Issue:
======
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
vulnerabilities:



 - 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
Computer zone.


 - 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
previewed.


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.


Mitigating Factors:
====================
 - 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
attacker's site.
 - Code that executed on the system would only run under the
privileges of the logged-on user.


Risk Rating:
============
 - Critical


Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read
   the Security Bulletins at:


   http://www.microsoft.com/technet/security/bulletin/ms03-
032.asp
   http://www.microsoft.com/security/security_bulletins/ms03-
032.asp


   for information on obtaining this patch.


Acknowledgment:
===============
 - Microsoft thanks  the following for working with us to protect
customers:


 - 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
to us.


 - 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.


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