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WMF Image Parsing Memory Corruption (MS06-004)
------------------------------------------------------------------------
SUMMARY
Internet Explorer has a remote code execution due to the way Windows
processes Metafile (WMF) images.
A specially crafted WMF image could potentially allow remote code
execution if a user visited a malicious Web site, opened or previewed an
e-mail message, or opened a specially crafted attachment in e-mail.
Allowing the attacker complete control of the affected system.
Note that this vulnerability in Internet Explorer is separate from the
vulnerabilities addressed in Windows in MS05-053 and MS06-001.
DETAILS
Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4
* Internet Explorer 5.01 Service Pack 4 on Microsoft Windows 2000 Service
Pack 4 <http://www.microsoft.com/technet/security/Bulletin/MS06-004.mspx>
Download the update
Immune Systems:
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
* Microsoft Windows XP Professional x64 Edition
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with Service Pack 1 for Itanium-based Systems
* Microsoft Windows Server 2003 x64 Edition family
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and
Microsoft Windows Millennium Edition (ME) Review the FAQ section of this
bulletin for details about these operating systems.
Mitigating Factors for WMF Image Parsing Memory Corruption Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0020>
CVE-2006-0020:
* 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. Also, Web
sites that accept or host user-provided content or advertisements, and
compromised Web sites, may contain malicious 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 request that takes
users to the attacker s Web site.
* In an e-mail based attack of this exploit, customers would have to open
a malicious e-mail message, preview a malicious e-mail message in the
Outlook Express preview pane, click on a link that would take them to a
malicious Web site, or open an attachment that could exploit the
vulnerability. Users can disable the preview pane in Outlook Express and
delete the suspicious e-mail message without opening the e-mail message.
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 an e-mail based attack of this exploit, customers would have to open
a malicious e-mail message, preview a malicious e-mail message in the
Outlook preview pane, click on a link that would take them to a malicious
Web site, or open an attachment that could exploit the vulnerability.
Users can disable the preview pane in Outlook and delete the suspicious
e-mail message without opening the e-mail message. Customers who read
e-mail in plain text in Outlook would have to click on a link that would
take them to a malicious Web site, or open an attachment to be at risk
from this vulnerability.
* Customers who have installed
<http://www.microsoft.com/windows/ie/downloads/critical/ie6sp1/default.mspx>
Internet Explorer 6 Service Pack 1 are not affected by this vulnerability and
are also not affected by exploits attempting to utilize this vulnerability
using the e-mail mail vector.
* Internet Explorer 6 Service Pack 1 is the only supported version for
Windows 98, Windows 98 Second Edition, and Windows Millennium.
* This issue does not affect Windows XP Service Pack 1, Windows XP
Service Pack 2, Windows XP Professional x64 Edition, Windows Server 2003,
Windows Server 2003 Service Pack 1, Windows Server 2003 for Itanium-based
Systems, Windows Server 2003 with Service Pack 1 for Itanium-based
Systems, or Windows Server 2003 x64 Edition. These Windows versions
include Internet Explorer 6 Service Pack 1 or later versions.
Workarounds for WMF Image Parsing Memory Corruption Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0020>
CVE-2006-0020:
No workarounds have been identified for this vulnerability.
Customers using Windows 2000 Service pack 4 with Internet Explorer 5.01
Service Pack 4 are strongly encouraged to apply the update or install
<http://www.microsoft.com/windows/ie/downloads/critical/ie6sp1/default.mspx>
Internet Explorer 6 Service Pack 1.
FAQ for WMF Image Parsing Memory Corruption Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0020>
CVE-2006-0020:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could remotely 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.
What causes the vulnerability?
When Internet Explorer displays a Web page that contains a specially
crafted WMF image, system memory may be corrupted in such a way that an
attacker could execute arbitrary code.
What is the Windows Metafile (WMF) image format?
A Windows Metafile (WMF) image is a 16-bit metafile format that can
contain both vector information and bitmap information. It is optimized
for the Windows operating system.
For more information about image types and formats, see
<http://support.microsoft.com/kb/320314> Microsoft Knowledge Base Article
320314 or visit the M
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdicpp/GDIPlus/AboutGDIPlus/ImagesBitmapsandMetafiles/Metafiles.asp>
SDN Library Web site.
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 by posting a specially
crafted WMF image on a Web site?
An attacker could host a malicious Web site that is designed to exploit
this vulnerability through Internet Explorer and then persuade a user to
view the Web site. This can also include Web sites that accept
user-provided content or advertisements, Web sites that host user-provided
content or advertisements, and compromised Web sites. These Web sites
could contain malicious Windows Metafile (WMF) images 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 in an Instant Messenger request that
takes users to the attacker's Web site. It could also be possible to
display specially crafted Web content by using banner advertisements or by
using other methods to deliver Web content to affected systems.
Could this vulnerability be exploited through other vectors?
Yes. An attacker could, for example, embed a specially crafted WMF image
in an e-mail message.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and visits a Web site
for any malicious action to occur. Therefore, any systems where Internet
Explorer is used frequently, such as workstations or terminal servers, are
at the most risk from this vulnerability.
What does the update do?
The update removes the vulnerability by modifying the way that Internet
Explorer validates the length of a message before it passes the message to
the allocated buffer.
Does this vulnerability affect image formats other than Windows Metafile
(WMF)?
The only image format affected is the Windows Metafile (WMF) format. It is
possible, however, that an attacker could rename the file name extension
of a WMF file to that of a different image format. In this situation,
Internet Explorer could detect and render the file as a WMF image by using
its
<http://msdn.microsoft.com/library/default.asp?url=/workshop/networking/moniker/overview/appendix_a.asp>
MIME type detection functionality, which could allow exploitation.
Users can block file types by extension to provide additional defense in
depth safeguards. However, it is important for content filtering to be
performed on file headers that are associated with content downloaded from
the Internet or that are received in e-mail messages.
If I block .wmf images by extension, can this protect me against attempts
to exploit this vulnerability?
No. Internet Explorer does not determine file types by the file name
extensions that they use. Therefore, if an attacker alters the file name
extension of a WMF image, Internet Explorer could still render the file in
a way that could exploit the vulnerability.
Is this issue related to Microsoft Security Bulletin MS05-053 -
Vulnerabilities in Graphics Rendering Engine Could Allow Code Execution
(896424), which was released in November 2005?
No, these are different and separate issues.
Is this issue related to Microsoft Security Bulletin MS06-001 -
Vulnerabilities in Graphics Rendering Engine Could Allow Code Execution
(912919), which was released in January 2006?
No, these are different and separate issues.
Is this issue related to a public posting discussing specially crafted WMF
images that could potentially cause the application using the Windows
Graphics Rendering Engine to crash?
No, these are different and separate issues. That posting has been
discussed in the
<http://blogs.technet.com/msrc/archive/2006/01/09/417198.aspx> Microsoft
Security Response Center Blog
Are Windows 98, Windows 98 Second Edition, or Windows Millennium Edition
critically affected by the vulnerability that is addressed in this
security bulletin?
No. This vulnerability does not exist on Windows 98, on Windows 98 Second
Edition, or on Windows Millennium Edition with Internet Explorer 6 Service
Pack 1, which is the only supported version of Internet Explorer on these
versions of Windows. For more information about severity ratings, visit
the following Web site. Microsoft will provide security updates on the
operating systems that are affected and the severity rating is critical
through June 30, 2006. It should be a priority for customers who have
these operating system versions to migrate to supported versions to
prevent potential exposure to vulnerabilities. For more information about
the Windows Product Lifecycle, visit the following Microsoft Support
Lifecycle Web site.
What versions of Internet Explorer are affected by this vulnerability?
The vulnerability exists in Internet Explorer 5.01 Service Pack 4 on
Windows 2000.
When this security bulletin was issued, had this vulnerability been
publicly disclosed?
Yes. This vulnerability has been publicly disclosed. It has been assigned
Common Vulnerability and Exposure number CVE-2006-0020.
When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
No. Microsoft had seen examples of proof of concept code published
publicly but had not received any information to indicate that this
vulnerability had been publicly used to attack customers when this
security bulletin was originally issued.
ADDITIONAL INFORMATION
The information has been provided by Microsoft Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/Bulletin/MS06-004.mspx>
http://www.microsoft.com/technet/security/Bulletin/MS06-004.mspx
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