[NT] Vulnerability in Microsoft Word Allows Code Execution (MS08-009)

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Vulnerability in Microsoft Word Allows Code Execution (MS08-009)
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SUMMARY

This critical security update resolves one privately reported
vulnerability in Microsoft Word that could allow remote code execution if
a user opens a specially crafted Word file. An attacker who successfully
exploited this vulnerability could take complete control of an affected
system. An attacker could then install programs; view, change, or delete
data; or create new accounts with full user rights. 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.

This is a critical security update for supported editions of Microsoft
Office 2000 and an important security update for Microsoft Office XP,
Microsoft Office 2003, and Microsoft Office Word Viewer 2003. For more
information, see the subsection, Affected and Non-Affected Software, in
this section.

DETAILS

Affected Software
Office Suite and Other Software - Component Maximum Security Impact -
Aggregate Severity Rating - Bulletins Replaced by This Update
* Microsoft Office 2000 Service Pack 3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=A513069B-8244-48E9-B136-01DDD3862802> Microsoft Word 2000 Service Pack 3 (KB943990) - Remote Code Execution - Critical - MS07-060
* Microsoft Office XP Service Pack 3 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=78C338AA-E410-4422-9E36-562F70D742E9> Microsoft Word 2002 Service Pack 3 (KB943957) - Remote Code Execution - Important - MS07-060
* Microsoft Office 2003 Service Pack 2 -
<http://www.microsoft.com/downloads/details.aspx?FamilyId=85CB1AA5-211F-4652-827B-2E79B8FFC2FC> Microsoft Word 2003 Service Pack 2 (KB943983) - Remote Code Execution - Important - MS07-024
*
<http://www.microsoft.com/downloads/details.aspx?FamilyId=FD4DDECD-ABD6-4783-B300-32B9D4BAD22A> Microsoft Office Word Viewer 2003 (KB943992) - - Remote Code Execution - Important - MS07-024

Non-Affected Software
* Office Suite and Other Software
* Microsoft Office 2003 Service Pack 3
* Microsoft Office Word Viewer 2003 Service Pack 3
* 2007 Microsoft Office System
* 2007 Microsoft Office System Service Pack 1
* Microsoft Office 2004 for Mac
* Microsoft Office 2008 for Mac

Word Memory Corruption Vulnerability - CVE-2008-0109
A remote code execution vulnerability exists in the way that Word handles
specially crafted Word files. The vulnerability could allow remote code
execution if a user opens a specially crafted Word file that includes a
malformed value. An attacker who successfully exploited this vulnerability
could take complete control of an affected system. An attacker could then
install programs; view, change, or delete data; or create new accounts
with full user rights.

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0109>
CVE-2008-0109

* Mitigating Factors for Word Memory Corruption Vulnerability
CVE-2008-0109
Mitigation refers to a setting, common configuration, or general
best-practice, existing in a default state, that could reduce the severity
of exploitation of a vulnerability. The following mitigating factors may
be helpful in your situation:

* The vulnerability cannot be exploited automatically through e-mail. For
an attack to be successful, a user must open an attachment that is sent in
an e-mail message.

* 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.

* 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.

* Users who have installed and are using the Office Document Open
Confirmation Tool for Office 2000 will be prompted with Open, Save, or
Cancel before opening a document. The features of the Office Document Open
Confirmation Tool are incorporated in Office XP and later editions of
Office.

Workarounds for Word Memory Corruption Vulnerability CVE-2008-0109
Workaround refers to a setting or configuration change that does not
correct the underlying vulnerability but would help block known attack
vectors before you apply the update. Microsoft has tested the following
workarounds and states in the discussion whether a workaround reduces
functionality:

* Use the Microsoft Office Isolated Conversion Environment (MOICE) when
opening files from unknown or un-trusted sources

The Microsoft Office Isolated Conversion Environment (MOICE) when added to
the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint
2007 File Formats is used to more securely open Word, Excel, and
PowerPoint binary format files.

To install MOICE, you must have Office 2003 or 2007 Office installed.

To install MOICE, you must have the Compatibility Pack for Word, Excel,
and PowerPoint 2007 File Formats. The compatibility pack is available as a
free download from the Microsoft Download Center:

Download the
<http://www.microsoft.com/downloads/details.aspx?FamilyID=941b3470-3ae9-4aee-8f43-c6bb74cd1466&displaylang=en> FileFormatConverters.exe package now

MOICE requires all updates that are recommended for all Office programs.
Visit Microsoft Update to install all recommended updates:

<http://update.microsoft.com/microsoftupdate/v6/default.aspx?ln=en-us>
http://update.microsoft.com/microsoftupdate/v6/default.aspx?ln=en-us

To enable MOICE, change the registered handle for the .doc file format.
The following table describes the command to enable or to disable MOICE
for the .doc file format:
Command to use to enable MOICE to be the registered handler - Command to
use to disable MOICE as the registered handler

ASSOC .doc=oice.word.document - ASSOC .doc=Word.Document.8

For more information on MOICE, see the following Microsoft Knowledge Base
Article 935865.

Impact of Workaround: Office 2003 and earlier formatted documents that are
converted to the 2007 Microsoft Office System Open XML format by MOICE
will not retain macro functionality. Additionally, documents with
passwords or that are protected with Digital Rights Management cannot be
converted.

* Use Microsoft Office File Block policy to prevent the opening of Office
2003 and earlier documents from unknown or untrusted sources and
locations.

The following registry scripts can be used to set the File Block policy.

Note Modifying the Registry incorrectly can cause serious problems that
may require you to reinstall your operating system. Microsoft cannot
guarantee that problems resulting from incorrect modification of the
Registry can be solved. Modify the Registry at your own risk.

For Office 2003
Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Word\Security\FileOpenBlock]

"BinaryFiles"=dword:00000001

Note In order to use 'FileOpenBlock' with Office 2003, all of the latest
Office 2003 security updates as of May 2007 must be applied.

Impact of Workaround: Users who have configured the File Block policy and
have not configured a special exempt directory as discussed in Microsoft
Knowledge Base Article 922848 will be unable to open Office 2003 files or
earlier versions in Office 2003 or 2007 Microsoft Office System.

Rollback
Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Word\Security\FileOpenBlock]

"BinaryFiles"=dword:00000000

* Do not open or save Microsoft Office files that you receive from
untrusted sources or that you receive unexpectedly from trusted sources.
This vulnerability could be exploited when a user opens a specially
crafted file.

FAQ for Word Memory Corruption Vulnerability - CVE-2008-0109
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could take complete control of
an affected system. An attacker could then install programs; view, change,
or delete data; or create new accounts with full user rights.

What causes the vulnerability?
The vulnerability is caused by a memory calculation error when parsing a
specially crafted Word file. The error may corrupt system memory in such a
way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take
complete control of an affected system. If a user is logged on with
administrative user rights, an attacker could take complete control of the
affected system. An attacker could then install programs; view, change, or
delete data; or create new accounts with full user rights. 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.

How could an attacker exploit the vulnerability?
This vulnerability requires that a user open a specially crafted Word file
with an affected version of Microsoft Word.

* In an e-mail attack scenario, an attacker could exploit the
vulnerability by sending a specially-crafted Word file to the user and by
convincing the user to open the file.

* In a Web-based attack scenario, an attacker would have to host a Web
site that contains a Word file that is used to attempt to exploit this
vulnerability. In addition, compromised Web sites and Web sites that
accept or host user-provided content could contain specially crafted
content that could exploit this vulnerability. An attacker would have no
way to force users to visit a specially crafted Web site. Instead, an
attacker would have to convince them to visit the Web site, typically by
getting them to click a link in an e-mail message or Instant Messenger
message that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability?
Systems where Microsoft Word is used are primarily at risk. Servers could
be at more risk if administrators allow users 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 Word calculates
the required memory allocation when opening Word files.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure. Microsoft had not received any information to
indicate that this vulnerability had been publicly disclosed when this
security bulletin was originally issued. This security bulletin addresses
the privately 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?
No. Microsoft had not received any information to indicate that this
vulnerability had been publicly used to attack customers and had not seen
any examples of proof of concept code published when this security
bulletin was originally issued.


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/ms08-009.mspx>
http://www.microsoft.com/technet/security/bulletin/ms08-009.mspx



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