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Vulnerability in Embedded Web Fonts Allows Code Execution (MS06-002)
------------------------------------------------------------------------
SUMMARY
A remote code execution vulnerability exists in Windows because of the way
that it handles malformed embedded Web fonts. An attacker could exploit
the vulnerability by constructing a malicious embedded Web font that could
potentially allow remote code execution if a user visited a malicious Web
site or viewed a specially crafted e-mail message. An attacker who
successfully exploited this vulnerability could take complete control of
an affected system.
DETAILS
Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4
<http://www.microsoft.com/downloads/details.aspx?FamilyId=DC6C2FE8-3C81-4661-994B-4146775BF590>
Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
<http://www.microsoft.com/downloads/details.aspx?FamilyId=6DAEA2AF-3723-4CDF-B5BD-B21AC75B5243>
Download the update
* Microsoft Windows XP Professional x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=1990B2CF-AE88-4849-AEAB-3F833969E197>
Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
<http://www.microsoft.com/downloads/details.aspx?FamilyId=5FC12654-486F-45BF-8D34-BDF0998869C5>
Download the update
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft
Windows Server 2003 with SP1 for Itanium-based Systems
<http://www.microsoft.com/downloads/details.aspx?FamilyId=E39D2E29-8934-4AA1-844D-11EFA57D9CC5>
Download the update
* Microsoft Windows Server 2003 x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=80B05C56-5BCE-4262-8142-AF0D8A7BC388>
Download the update
* 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.
A remote code execution vulnerability exists in Windows because of the way
that it handles malformed embedded Web fonts. An attacker could exploit
the vulnerability by constructing a malicious embedded Web font that could
potentially allow remote code execution if a user visited a malicious Web
site or viewed a specially crafted e-mail message. An attacker who
successfully exploited this vulnerability could take complete control of
an affected system.
Mitigating Factors for Windows Embedded Web Font Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0010>
CVE-2006-0010:
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 or Instant Messenger request 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.
By default, Internet Explorer on Windows Server 2003 runs in a restricted
mode that is known as
<http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp>
Enhanced Security Configuration. This mode mitigates this vulnerability where
the e-mail vector is concerned although clicking on a link would still put
users at risk. In Windows Server 2003, Microsoft Outlook Express uses plain
text for reading and sending messages by default. When replying to an e-mail
message that is sent in another format, the response is formatted in plain
text. See the FAQ section of this vulnerability for more information about
Internet Explorer Enhanced Security Configuration.
Workarounds for Windows Embedded Web Font Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0010>
CVE-2006-0010:
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.
* Read e-mail messages in plain text format if you are using Outlook 2002
or a later version, or Outlook Express 6 SP1 or a later version, to help
protect yourself from the HTML e-mail attack vector.
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or
a later version and Microsoft Outlook Express 6 users who have applied
Internet Explorer 6 Service Pack 1 or a later version can enable this
setting and view e-mail messages that are not digitally signed or e-mail
messages that are not encrypted in plain text only.
Digitally signed e-mail messages or encrypted e-mail messages are not
affected by the setting and may be read in their original formats. For
more information about how to enable this setting in Outlook 2002, see
<http://support.microsoft.com/kb/307594> Microsoft Knowledge Base Article
307594.
For information about this setting in Outlook Express 6, see
<http://support.microsoft.com/kb/291387> Microsoft Knowledge Base Article
291387.
Impact of Workaround: E-mail messages that are viewed in plain text format
will not contain pictures, specialized fonts, animations, or other rich
content. Additionally:
* The changes are applied to the preview pane and to open messages.
* Pictures become attachments so that they are not lost.
* Because the message is still in Rich Text or HTML format in the store,
the object model (custom code solutions) may behave unexpectedly.
* Configure Font Download to Prompt or Disable in the Internet and
Local Intranet Zones.
Impact of Workaround: Web sites that depend on embedded fonts may fail to
render.
1. From within Internet Explorer, Click on the Tools menu then click
Internet Options.
2. Click on the Security Tab.
3. To change the setting for the Internet zone select Internet and press
the Custom Level button.
4. Scroll down to the Downloads section and select Prompt or Disable for
the Font Download security setting.
5. Press OK to close the Security Settings dialog box.
6. Press OK to close the Internet Options dialog box.
FAQ for Windows Embedded Web Font Vulnerability -
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0010>
CVE-2006-0010:
What is the scope of the vulnerability?
If a user is logged on with administrative user rights, 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.
What causes the vulnerability?
When Windows displays a specially formed embedded Web font, it 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 the affected system.
How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by creating a malicious Web
page or an HTML e-mail message and then persuading the user to visit the
page or to view the HTML e-mail message. If the user visited the page or
viewed the e-mail message, the attacker could access information from
other Web sites, could access local files in predetermined locations on
the system, or could cause malicious code to run in the security context
of the locally logged on user. An attacker could also try to compromise a
Web site and have it display malicious content. Additionally, 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.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and reading e-mail or
visiting Web sites for any malicious action to occur. Therefore, any
systems where e-mail is read or where Internet Explorer is used
frequently, such as workstations or terminal servers, are at the most risk
from this vulnerability. Systems that are not typically used to read
e-mail or to visit Web sites, such as most server systems, are at a
reduced risk.
I am running Internet Explorer on Windows Server 2003. Does this mitigate
this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as
<http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp>
Enhanced Security Configuration. This mode mitigates this vulnerability where
the e-mail vector is concerned although clicking on a link would still put
users at risk. In Windows Server 2003, Microsoft Outlook Express uses plain
text for reading and sending messages by default. When replying to an e-mail
message that is sent in another format, the response is formatted in plain text.
What is Internet Explorer Enhanced Security Configuration?
Internet Explorer
<http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp>
Enhanced Security Configuration is a group of preconfigured Internet Explorer
settings that reduce the likelihood of a user or of an administrator
downloading and running malicious Web content on a server. Internet Explorer
<http://msdn.microsoft.com/library/default.asp?url=/workshop/security/szone/overview/esc_changes.asp>
Enhanced Security Configuration reduces this risk by modifying many
security-related settings. This includes the settings on the Security tab and
the Advanced tab in the Internet Options dialog box. Some of the important
modifications include the following:
* Security level for the Internet zone is set to High. This setting
disables scripts, ActiveX controls, Microsoft Java Virtual Machine
(MSJVM), and file downloads.
* Automatic detection of intranet sites is disabled. This setting assigns
all intranet Web sites and all Universal Naming Convention (UNC) paths
that are not explicitly listed in the Local intranet zone to the Internet
zone.
* Install On Demand and non-Microsoft browser extensions are disabled.
This setting prevents Web pages from automatically installing components
and prevents non-Microsoft extensions from running.
* Multimedia content is disabled. This setting prevents music,
animations, and video clips from running.
What does the update do?
The update removes the vulnerability by modifying the way that Windows
validates the length of a message before it passes the message to the
allocated buffer when handling embedded Web fonts.
When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.
ADDITIONAL INFORMATION
The information has been provided by Microsoft Security.
The original article can be found at:
<http://www.microsoft.com/technet/security/Bulletin/MS06-002.mspx>
http://www.microsoft.com/technet/security/Bulletin/MS06-002.mspx
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