[NT] Vulnerability in Microsoft Visual Basic for Applications Allows Code Execution (MS06047)



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Vulnerability in Microsoft Visual Basic for Applications Allows Code
Execution (MS06047)
------------------------------------------------------------------------


SUMMARY

A remote code execution vulnerability exists in the way that Visual Basic
for Applications (VBA) checks the document properties that a host
application passes to it when opening a document. This vulnerability could
allow an attacker who successfully exploited the vulnerability to take
complete control of the affected system.

DETAILS

Affected Software:
* Microsoft Office 2000 Service Pack 3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=837A4FA9-FABC-4119-9AAF-2C8663029D2B> Download the update (KB920822)
* Microsoft Project 2000 Service Release 1 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=744DD25D-B9A7-4E30-B64E-1C9BB0F87D90> Download the update (KB920822)
* Microsoft Access 2000 Runtime Service Pack 3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=ED5A8C40-C592-4299-AFB2-5F0F6E2B1DCD> Download the update (KB920822)
* Microsoft Office XP Service Pack 3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B26ADC3C-1DB8-46FD-8381-B199EE351E7C> Download the update (KB920821)
* Microsoft Project 2002 Service Pack 1 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=62EF50AA-6061-4185-9713-F8C31B195103> Download the update (KB920821)
* Microsoft Visio 2002 Service Pack 2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=43525B6A-58B7-49C7-88D8-4983D1614A96> Download the update (KB920821)

Microsoft Works Suites:
* Microsoft Works Suite 2004 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B26ADC3C-1DB8-46FD-8381-B199EE351E7C> Download the update (KB920821) (same as the Microsoft Office XP update)
* Microsoft Works Suite 2005 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B26ADC3C-1DB8-46FD-8381-B199EE351E7C> Download the update (KB920821) (same as the Microsoft Office XP update)
* Microsoft Works Suite 2006 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=B26ADC3C-1DB8-46FD-8381-B199EE351E7C> Download the update (KB920821) (same as the Microsoft Office XP update)
* Microsoft Visual Basic for Applications SDK 6.0 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=424DF92A-3CC4-4B72-B2F8-D45ED2A8F4B3> Download the update (KB923167)
* Microsoft Visual Basic for Applications SDK 6.2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=424DF92A-3CC4-4B72-B2F8-D45ED2A8F4B3> Download the update (KB923167)
* Microsoft Visual Basic for Applications SDK 6.3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=424DF92A-3CC4-4B72-B2F8-D45ED2A8F4B3> Download the update (KB923167)
* Microsoft Visual Basic for Applications SDK 6.4 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=424DF92A-3CC4-4B72-B2F8-D45ED2A8F4B3> Download the update (KB923167)

Non-Affected Software:
* Microsoft Office 2003 Service Pack 1 and Microsoft Office 2003 Service
Pack 2

Mitigating Factors for Visual Basic for Applications Vulnerability -
CVE-2006-3649:
* An attacker who successfully exploited this vulnerability could gain
the same user rights as the local user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.

* In Outlook 2002 and Outlook 2003, the vulnerability could not be
exploited automatically through e-mail. A user would have to click on an
attachment and then acknowledge a warning and accept a prompt to Open
before the vulnerability could be exploited.

* In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit this vulnerability. In
addition, compromised Web sites and Web sites that accept or host
user-provided content or advertisements could contain specially crafted
content that could exploit this vulnerability. In all cases, however, an
attacker would have no way to force users to visit these Web sites.
Instead, an attacker would have to persuade users to visit the Web site,
typically by getting them to click a link in an e-mail message or instant
messenger message that takes users to the attacker's Web site.

Note Office 2000 products do not prompt the user to Open, Save, or Cancel
before opening a document.

Workarounds for Visual Basic for Applications Vulnerability -
CVE-2006-3649:
Microsoft has tested the following workarounds. While these workarounds
will not correct the underlying vulnerability, they help block known
attack vectors. When a workaround reduces functionality, it is identified
in the following section.

Do not open or save Microsoft Office files that you receive from
un-trusted sources or that you received unexpectedly from trusted sources.

This vulnerability could be exploited when a user opens a file.

FAQ for Visual Basic for Applications Vulnerability - CVE-2006-3649:
What is the scope of the vulnerability?
A remote code execution vulnerability exists in the way that Visual Basic
for Applications (VBA) checks document properties that a host application
passes to it when opening a document. This vulnerability could allow an
attacker who successfully exploited this vulnerability to take complete
control of the affected system.

What causes the vulnerability?
The vulnerability results from the way that VBA checks certain document
properties that a host application passes to it when opening a document.
As a result, it is possible for the host application to pass unchecked
parameters to VBA, causing a buffer overrun condition that could allow
arbitrary code to be executed.

What is Visual Basic for Applications (VBA)?
Microsoft VBA is a development technology for developing client desktop
packaged applications and integrating them with existing data and systems.
Microsoft VBA is based on the Microsoft Visual Basic development system.
Microsoft Office products include VBA and make use of VBA to perform
certain functions. VBA can also be used to build customized applications
based around an existing host application.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take
complete control of the affected system.

How could an attacker exploit the vulnerability?
In order for an attack to be successful, a user would have to open a
specially crafted document sent to them by an attacker. This document
could be any type of document that supports VBA, such as a Word document,
Excel spreadsheet, PowerPoint presentation. In the case where Microsoft
Word is being used as the HTML e-mail editor for Microsoft Outlook, this
document could be an e-mail message; however, the user would need to reply
to or forward the message in order for the vulnerability to be exploited.

In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit this vulnerability. In
addition, compromised Web sites and Web sites that accept or host
user-provided content or advertisements could contain specially crafted
content that could exploit this vulnerability. In all cases, however, an
attacker would have no way to force users to visit these Web sites.
Instead, an attacker would have to persuade users to visit the Web site,
typically by getting them to click a link in an e-mail message or instant
messenger message that takes users to the attacker's Web site.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be
at more risk if users who have sufficient administrative permissions are
given the ability to log on to servers and to run programs. However, best
practices strongly discourage allowing this.

What does the update do?
The update removes the vulnerability by modifying the way that Visual
Basic for Applications parses the function before it passes the message to
the allocated buffer.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
Yes. While the initial report was provided through responsible disclosure,
the vulnerability was later disclosed publicly. This security bulletin
addresses the publicly disclosed vulnerability as well as additional
issues discovered through internal investigations.

When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
Yes. When the security bulletin was released, Microsoft had received
information that this vulnerability was being exploited.


ADDITIONAL INFORMATION

The information has been provided by Microsoft Product Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/Bulletin/MS06-047.mspx>
http://www.microsoft.com/technet/security/Bulletin/MS06-047.mspx



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