Microsoft Security Bulletin MS01-015

[Microsoft Product Security <secnotif () MICROSOFT COM>]

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Title:      IE can Divulge Location of Cached Content
Date:       06 March 2001
Software:   IE and Windows Scripting Host
Impact:     Run code of attacker's choice. Three other
            vulnerabilities, of lesser severity and exploitable in
            more restricted circumstances, also are eliminated by
            the patches.
Bulletin:   MS01-015

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-015.asp.
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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 Scripting Host rather than IE. Because
   it could only be exploited via IE, we have provided the patch
   here. 
 - 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(r) 4.0 or Windows(r) 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.

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