Microsoft Security Bulletin (MS00-081)
Patch Available for New Variant of "VM File Reading" Vulnerability
Originally posted: October 25, 2000
Microsoft has released a patch that eliminates a security
vulnerability in the Microsoft(r) virtual machine (Microsoft VM)
that originally was discussed in Microsoft Security Bulletin
MS00-011. Like the original vulnerability, the new variant could
enable a malicious web site operator to read files from the computer
of a person who visited his site or read web content from inside an
intranet if the malicious site was visited by a computer from within
Frequently asked questions regarding this vulnerability and the
patch can be found at
The Microsoft VM is a virtual machine for the Win32(r) operating
environment. It runs atop Microsoft Windows(r) 95, 98, Me, Windows
NT(r) 4.0, and Windows 2000. It ships as part of each operating
system, and also as part of Microsoft Internet Explorer.
The version of the Microsoft VM that ships with Microsoft Internet
Explorer 4.x and Internet Explorer 5.x contains a security
vulnerability that could allow a Java applet to operate outside the
bounds set by the sandbox. A malicious user could write a Java
applet that could read - but not change, delete or add - files from
the computer of a person who visited his site or read web content
from inside an intranet if the malicious site is visited by a
computer from within that intranet.
The vulnerability at issue here is a new variant of the vulnerability
originally discussed in Microsoft Security Bulletin MS00-011. The
only significant difference between the new and original variants
lies in the specific programming technique used to exploit the
vulnerability; in other respects, the two are virtually identical.
Applying the new patch eliminates both the new and original
Affected Software Versions
Versions of the Microsoft VM are identified by build numbers, which
can be determined using the JVIEW tool, as discussed in the FAQ. The
following builds of the Microsoft VM are affected:
- All builds in the 2000 series.
- All builds in the 3000 series.
Note: The Microsoft VM ships as part of several products. However,
the primary ship vehicle is Internet Explorer.
New versions of the Microsoft VM that include a fix for the
vulnerability can be downloaded from the following locations:
- 2000-series builds:
A patch specifically for the 2000-series builds will be available
shortly. Customers who wish to eliminate the vulnerability can
also do so by upgrading to build 3319 at
Upgrade to build 3319 or later at
Note: 2000-series builds are shipped as part of Internet Explorer
4.x; 3000 series builds are shipped as part of Internet Explorer
5.x. However, customers may upgrade the Microsoft VM on their
machines independent of the browser, and the Microsoft VM also ships
as part of many other applications, so it is possible for the actual
build number to be higher than the one associated with the version
of IE that is installed on the machine. In such cases, customers
should determine what version of the patch to install based on the
build number, not on the version of IE.
Note: Additional security patches are available at the Microsoft
Please see the following references for more information related to
- Frequently Asked Questions: Microsoft Security Bulletin MS00-081,
- Microsoft Security Bulletin MS00-011,
- Microsoft Knowledge Base article Q277014 discusses this issue and
will be available soon.
- Microsoft TechNet Security web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Product Support Services is available at
- October 25, 2000: Bulletin Created.
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Last Updated October 25, 2000