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Title:      Flaw in Microsoft VM Could Enable System 
            Compromise (810030)
Date:       11 December 2002 
Software:   Microsoft VM
Impact:     Eight vulnerabilities, the most serious of which
            would enable an attacker to gain control over
            another user's system.
Max Risk:   Critical 
Bulletin:   MS02-069

Microsoft encourages customers to review the Security Bulletins at: 
http://www.microsoft.com/technet/security/bulletin/MS02-069.asp
http://www.microsoft.com/security/security_bulletins/ms02-069.asp. 
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Issue:
======
The Microsoft VM is a virtual machine for the Win32(r) operating
environment. The Microsoft 
VM shipped in most versions of Windows (a complete list is available
in the FAQ), as well as 
in most versions of Internet Explorer. 

A new version of the Microsoft VM is available, which includes all
previously released fixes 
for the VM, as well as fixes for eight newly reported security
issues. The attack vectors 
for all of the new issues would likely be the same. An attacker would
create a web page 
that, when opened, exploits the desired vulnerability, and either
host it on a web page or 
send it to a user as an HTML mail. 

The newly reported security issues are as follows: 
 - A security vulnerability through which an untrusted
   Java applet could access COM objects. By design, COM
   objects should only be available to trusted Java
   programs because of the functionality they expose. COM
   objects are available that provide functionality through
   which an attacker could take control of the system. 
 - A pair of vulnerabilities that, although having 
   different underlying causes, would have the same effect,
   namely, disguising the actual location of the applet's
   codebase. By design, a Java applet that resides on user
   storage or a network share has read access to the folder
   it resides in and all folders below it. The 
   vulnerabilities provide methods by which an applet 
   located on a web site could misrepresent the location of
   its codebase, to indicate that it resided instead on the
   user's local system or a network share. 
 - A vulnerability that could enable an attacker to construct
   an URL that, when parsed, would load a Java applet from
   one web site but misrepresent it as belonging to another
   web site. The result would be that the attacker's applet
   would run in the other site's domain. Any information the
   user provided to it could be relayed back to the attacker. 
 - A vulnerability that results because the Microsoft VM 
   doesn't prevent applets from calling the JDBC APIs - a 
   set of APIs that provide database access methods. By 
   design, these APIs provide functionality to add, change,
   delete or modify database contents, subject only to the
   user's permissions. 
 - A vulnerability through which an attacker could 
   temporarily prevent specified Java objects from being
   loaded and run. A legacy security mechanism known as the
   Standard Security Manager provides the ability to impose
   restrictions on Java applets, up to and including 
   preventing them from running altogether. However, the VM
   does not adequately regulate access to the SSM, with the
   result that an attacker's applet could add other Java 
   objects to the "banned" list. 
 - A vulnerability through which an attacker could learn a
   user's username on their local system. The vulnerability
   results because one particular system property, user.dir,
   should not be available to untrusted applets but, through
   a flaw, is. While knowing a username would not in itself
   pose a security risk, it could be useful for 
   reconnaissance purposes. 
 - A vulnerability that results because it's possible for a
   Java applet to perform an incomplete instantiation of 
   another Java object. The effect of doing so would be to
   cause the containing application - Internet Explorer - to
   fail.

Mitigating Factors:
====================
All of the vulnerabilities share a pair of common mitigating factors:
 - The web-based attack vector would be blocked if the user
   had disabled Java applets in the Internet Explorer
   security zone in which the attacker's web site rendered. 
 - The email vector would be blocked if the user were running
   any of several mail clients. Specifically, Outlook 
   Express 6 and Outlook 2002 (which ships as part of Office
   XP) disable Java by default, and Outlook 98 and 2000
   disable it if the Outlook Email Security Update has been
   installed. 

COM Object Access Vulnerability: 
 - The vulnerability represents a target of opportunity only. 
   The attacker would have no means of ensuring that 
   sensitive data would be located in system memory, cookies,
   the clipboard, or other locations. 

CODEBASE Spoofing Vulnerabilities: 
 - The attacker's access to files, including those on remote
   shares, would be limited to those of the user. If the
   user had only limited permissions, so would the attacker. 

Domain Spoofing Vulnerability: 
 - The vulnerability could only be exploited if the user
   visited the attacker's site en route to visiting a 
   third-party site. 
 - The effect of exploiting the vulnerability would apply
   only to the current web session. 

JDBC API Vulnerability: 
 - To exploit this vulnerability, the attacker would need
   to know the names of each data source he or she wanted
   to access. In most cases, this would require the attacker
   to have insider knowledge of the user's network. 
 - The attacker would gain only the user's own permissions
   to the data sources. For instance, if the user had only
   read access to a particular database, so would the
   attacker. 

Standard Security Manager Access Vulnerability: 
 - The effect of exploiting this vulnerability would only
   persist during the current browser session. 
 - The vulnerability provides no means of modifying an
   applet's functioning - only preventing it from running. 

User.dir Exposure Vulnerability: 
 - Knowing a user's username would not, by itself, enable
   an attacker to take any action against the user. The
   sole value in learning this information would be for
   reconnaissance purposes, in the hope of using it in
   some future, unspecified attack. 

Incomplete Java object Instantiation Vulnerability: 
 - This vulnerability would only enable the attacker to
   cause Internet Explorer to fail - it would not enable
   the attacker to cause Windows itself, or any other
   applications, to fail. 
 - The user could restore normal operation by restarting
   the browser.

Risk Rating:
============
 - COM Object Access Vulnerability: Critical 
 - CODEBASE Spoofing Vulnerabilities: Important 
 - Domain Spoofing Vulnerability: Moderate 
 - JDBC API Vulnerability: Moderate 
 - Standard Security Manager Access Vulnerability: Low 
 - User.dir Exposure Vulnerability: Low 
 - Incomplete Java object Instantiation Vulnerability: Low

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletin at
   http://www.microsoft.com/technet/security/bulletin/ms02-069.asp
   for information on obtaining this patch.

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