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[MS] Update: Schwachstelle in der IE Cache-Architektur - MS01-015



[[PGP Signed Part:Undecided]]
Liebe Kolleginnen und Kollegen,

soeben erreichte uns nachfolgendes Update zu einer Warnung des
Microsoft Product Security Notification Service ueber
Sicherheitsprobleme im "Windows Scripting Host".  Wir geben diese
Informationen unveraendert an Sie weiter.

Microsoft veroeffentlicht neue Versionen der Patches zum "Windows
Scripting Host", die einige in MS01-015 beschriebene Schwachstellen
beheben.

Beschreibung:
Beschrieben wird eine Schwachstelle in der Cache-Architektur des
Internet Explorer, durch die ein Angreifer durch eine praeparierte
Webseite die Lage des lokalen Caches auf der festplatte des Clients
ermitteln kann.

Diese Information ermoeglicht es dem Angreifer, kompilierte
Hilfe-Dateien (.CHM) auf dem Client zu starten, die Shortcuts zu
ausfuehrbaren Dateien enthalten koennen, die dann ebenfalls gestartet
werden.

Betroffen sind
        Microsoft Internet Explorer 5.01 
        Microsoft Internet Explorer 5.5 
        Microsoft Windows Scripting Host 5.1 
        Microsoft Windows Scripting Host 5.5

Lediglich die Dateien fuer den "Windows Scripting Host" wurden
ersetzt, die Service-Packs fuer den IE sind nach wie vor gueltig.

Das DFN-CERT bietet einen Mirror der Inhalte des FTP-Servers von
Microsoft mit den dort bereitgestellten Patches fuer die us-
amerikanische und deutsche Sprachversion von Microsoft Windows NT 4.0
und des Internet Explorers unter

    ftp://ftp.cert.dfn.de/pub/vendor/microsoft/

an. Des weiteren finden Sie dort die aktuellen Service-Packs (deutsch
und us-amerikanisch) fuer Windows NT 4.0 und die aktuellen Patches
fuer Windows 2000 (deutsch und us-amerikanisch).

Mit freundlichen Gruessen,
    Marco Thorbruegge, DFN-CERT
-- 
Marco Thorbruegge        |              mailto:thorbruegge@cert.dfn.de
DFN-CERT GmbH            |          http://www.cert.dfn.de/team/matho/
Oberstrasse 14b          |                    Phone: +49(40)808077-555
D-20144 Hamburg          |                      FAX: +49(40)808077-556
Germany                  | PGP-Key: finger thorbruegge@ftp.cert.dfn.de

----------------------------------------------------------------------
Title:      IE can Divulge Location of Cached Content
Released:   06 March 2001
Revised:    20 April 2001 (version 2.0)
Software:   Microsoft Windows Script Host 5.1 and 5.5
Impact:     Run code of attacker's choice
Bulletin:   MS01-015

Microsoft encourages customers to review the Security Bulletin at: 
http://www.microsoft.com/technet/security/bulletin/MS01-015.asp.
----------------------------------------------------------------------

Reason for Revision:
====================
A regression was found in the previously released Windows Script Host
patch referenced in the first version of this security bulletin.  We
have updated and re-released the Windows Script Host patch and have
updated the bulletin 
accordingly. The re-release only applies to changes with the Windows
Script Host patches available in the bulletin. No changes have been
made to the originally released Internet Explorer patches.

Customers who applied the Windows Script Host patch when this
bulletin was first released should download and apply the updated
Windows Script Host patch referenced in the bulletin.  Customers who
did not apply the Windows Script Host when this bulletin was first
released are encouraged to apply the Windows Script Host patch listed
in the bulletin.  

Issue:
======
The IE security architecture provides a caching mechanism that is
used 
to store content that needs to be downloaded and processed on the 
user's local machine. The purpose of the cache is to obfuscate the 
physical location of the cached content, in order to ensure that the 
web page or HTML e-mail will work through the IE security
architecture 
to access the information. This ensures that the uses of the 
information can be properly restricted. 

A vulnerability exists because it is possible for a web page or HTML
e- mail to learn the physical location of cached content. Armed with
this 
information, an attacker could cause the cached content to be opened
in 
the Local Computer Zone. This would enable him to launch compiled
HTML 
help (.CHM) files that contain shortcuts to executables, thereby 
enabling him to run the executables. 

In addition to eliminating this vulnerability, the patches provided 
below eliminate three other vulnerabilities that either pose 
significantly less risk or could only be exploited in very restricted
situations: 

A variant of the Frame Domain Verification vulnerability discussed in
Microsoft Security Bulletins MS00-033, MS00-055, and MS00-093. The 
vulnerability could enable a malicious web site operator to open two 
browser windows, one in the web site's domain and the other on the 
user's local file system, and to pass information from the latter to 
the former. This could enable the web site operator to read, but not 
change, any file on the user's local computer that could be opened in
a 
browser window. 

A vulnerability that is identical in effect to the Frame Domain 
Verification vulnerability, but which actually results from a flaw in
Windows Script Host rather than IE. Because it could only be
exploited 
via IE, we have provided the fix here. The fix that was released on 
March 06, 2001, was subsequently discovered to have a regression
error, 
and a corrected version was released on April 19, 2001. 

A vulnerability that affects how Telnet sessions are invoked via IE.
By 
design, telnet sessions can be launched via IE. However, a 
vulnerability exists because when doing so, IE will start Telnet
using 
any command-line options the web site specifies. This only becomes a 
concern when using the version of the Telnet client that installs as 
part of Services for Unix (SFU) 2.0 on Windows NT 4.0 or Windows 2000
machines. The version of the Telnet client in SFU 2.0 provides an 
option for creating a verbatim transcript of a Telnet session. An 
attacker could start a session using the logging option, then stream
an 
executable file onto the user's system in a location that would cause
it to be executed automatically the next time the user booted the 
machine. The flaw does not lie in the Telnet client, but in IE, which
should not allow Telnet to be started remotely with command-line 
arguments. 

Mitigating Factors:
====================
None of the vulnerabilities could be exploited without some user
action - either browsing to the attacker's site or opening a mail
from him.

 - Customers who exercise safe browsing habits would be less likely
   visit untrustworthy sites, and customers who have used the
Security 
   Zones feature to restrict what HTML mail can do would be less
likely to 
   be affected by this vulnerability. 

 - The variants of the "frame domain verification" vulnerability
discussed 
   above could only be used to view files, and only file types that
can be 
   opened in a browser window. 

 - The vulnerability affecting Telnet invocation is only a concern
for 
   customers who are using the Telnet client that ships as part of 
   Services for Unix 2.0. Other versions of Telnet do not include the
   command-line feature to create log files. 

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-015.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - Oliver Friedrichs of securityfocus.com (for reporting the Telnet
invocation issue)

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