Microsoft Security Bulletin (MS99-048)

[aleph1 () UNDERGROUND ORG (Aleph One)]

Microsoft Security Bulletin (MS99-048)
--------------------------------------

Patch Available for "Active Setup Control" Vulnerability
Originally Posted: November 11, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability that could
allow a malicious user to embed an unsafe executable within an email and
disguise it as a safe type of attachment. Through a complicated series of
steps, the unsafe executable could be made to execute under certain
conditions, if the user opened the attachment.

Frequently asked questions regarding this vulnerability can be found at
http://www.microsoft.com/security/bulletins/MS99-048faq.asp.

Issue
=====
A particular ActiveX control allows cabinet files to be launched and
executed. This could allow an HTML mail to contain a malicious
cabinet file, disguised as a file of an innocuous type. If a user
attempted to open this file, the operation would fail but could,
depending on the mail package, leave a copy of the file in a known
location. The ActiveX control could then be used via a script
embedded in the mail to launch the copy, thereby executing the
malicious code.

The vulnerability could only be exploited in cases where a mail reader were
used that allowed scripts in HTML mail and stored temporary copies of
launched programs in known locations. The patch restricts the ability of
the control to launch unsigned cabinet files that have been downloaded
from the local machine.

Affected Software Versions
==========================
The affected ActiveX control ships as part of Microsoft Internet Explorer 4
and 5

Patch Availability
==================
 - http://windowsupdate.microsoft.com
 - http://www.microsoft.com/msdownload
 - http://www.microsoft.com/msdownload/iebuild/ascontrol/en/ascontrol.htm

NOTE: Microsoft produces security patches for Internet Explorer 4.01 SP2
and higher. In the event that this package is applied to Internet Explorer
4.01  SP1, the package states that a fix is not needed. This message is
incorrect, as the vulnerability does exist on Internet Explorer 4.01 SP1.
If you are using Internet Explorer 4.01 SP1, please upgrade to the latest
version of Internet Explorer to resolve this issue.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-048: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-048faq.asp
 - Microsoft Knowledge Base (KB) article Q244540, Update Available
   for "Active Setup Control" Vulnerability,
   http://support.microsoft.com/support/kb/articles/q244/5/40.asp
   (Note: It may take 24 hours from the original posting of this
   bulletin for the KB article to be visible.)
 - Microsoft Security Advisor web site,
   http://www.microsoft.com/security/default.asp.

Obtaining Support on this Issue
===============================
This is a fully supported patch. Information on contacting Microsoft
Technical Support is available at
http://support.microsoft.com/support/contact/default.asp.

Acknowledgments
===============
Microsoft acknowledges Juan Carlos Garcia Cuartango of Spain for
bringing this issue to our attention.

Revisions
=========
 - November 11, 1999: Bulletin Created.

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