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Title: Flaw in Microsoft VM Could Enable System Compromise
(816093)
Date: 09 April 2003
Software: Microsoft VM
Impact: Allow attacker to execute code of his or her choice
Max Risk: Critical
Bulletin: MS03-011

Microsoft encourages customers to review the Security Bulletins
at:

http://www.microsoft.com/technet/security/bulletin/MS03-011.asp
http://www.microsoft.com/security/security_bulletins/ms03-011.asp

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Issue:

The Microsoft VM is a virtual machine for the Win32(r) operating
environment. The Microsoft VM is shipped in most versions of
Windows, as well as in most versions of Internet Explorer.

The present Microsoft VM, which includes all previously released
fixes to the VM, has been updated to include a fix for the newly
reported security vulnerability. This new security vulnerability
affects the ByteCode Verifier component of the Microsoft VM, and
results because the ByteCode verifier does not correctly check for
the presence of certain malicious code when a Java applet is being
loaded. The attack vector for this new security issue would likely
involve an attacker creating a malicious Java applet and inserting
it into a web page that when opened, would exploit the
vulnerability. An attacker could then host this malicious web page
on a web site, or could send it to a user in e-mail.

Mitigating Factors:

• • In order to exploit this vulnerability via the web-based attack
    vector, the attacker would need to entice a user into visiting a
    web site that the attacker controlled. The vulnerability themselves
    provide no way to force a user to a web site.
• • Java applets are disabled within the Restricted Sites Zone. As a
    result, any mail client that opened HTML mail within the Restricted
    Sites Zone, such as Outlook 2002, Outlook Express 6, or Outlook 98
    or 2000 when used in conjunction with the Outlook Email Security
    Update, would not be at risk from the mail-based attack vector.
• • The vulnerability would gain only the privileges of the user, so
    customers who operate with less than administrative privileges
    would be at less risk from the vulnerability.
• • Corporate IT administrators could limit the risk posed to their
    users by using application filters at the firewall to inspect and
    block mobile code.

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/ms03-011.asp
http://www.microsoft.com/security/security_bulletins/ms03-11.asp

for information on obtaining this patch.

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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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