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Vulnerability in Windows Explorer Allows Execution (MS06-057)
------------------------------------------------------------------------
SUMMARY
A remote code execution vulnerability exists in Windows Shell due to
improper validation of input parameters when invoked by the
WebViewFolderIcon ActiveX control (Web View). This vulnerability could
potentially allow remote code execution if a user visited a specially
crafted Web site or viewed a specially crafted e-mail message. An attacker
could exploit the vulnerability by hosting a web site that contained a web
page that was used to exploit this vulnerability. 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=756f53a7-28dc-422a-a691-c1bbfcbf3d0c>
Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service
Pack 2
<http://www.microsoft.com/downloads/details.aspx?FamilyId=235bca55-8d43-4eaf-8970-a55bc3165e3d>
Download the update
* Microsoft Windows XP Professional x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=96271f96-0d8e-4ab1-b131-2b37fca7e6e7>
Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service
Pack 1
<http://www.microsoft.com/downloads/details.aspx?FamilyId=48f2314b-b268-468c-919c-593e06af4453>
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=6507e201-b84e-432a-8797-23b586ad15ae>
Download the update
* Microsoft Windows Server 2003 x64 Edition
<http://www.microsoft.com/downloads/details.aspx?FamilyId=2b39693f-aabc-49c6-9d1a-6791f80f8f22>
Download the update
Note: The security updates for Microsoft Windows Server 2003, Windows
Server 2003 Service Pack 1, and Windows Server 2003 x64 Edition also apply
to Windows Server 2003 R2.
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-3730>
CVE-2006-3730
Mitigating Factors for Windows Shell Remote Code Execution Vulnerability:
* In a Web-based attack scenario, an attacker would have to host a Web
site that contained a Web page that was used to 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 persuade
them to visit the Web site, typically by getting them to click a link that
takes them 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. See
the FAQ section of this security update for more information about Internet
Explorer Enhanced Security Configuration.
Workarounds for Windows Shell Remote Code Execution Vulnerability:
* Prevent the WebViewFolderIcon ActiveX object from running in Internet
Explorer.
You can disable attempts to instantiate an ActiveX control in Internet
Explorer by setting the kill bit for the control in the registry.
Warning If you use Registry Editor incorrectly, you may cause serious
problems that may require you to reinstall your operating system.
Microsoft cannot guarantee that you can solve problems that result from
using Registry Editor incorrectly. Use Registry Editor at your own risk.
For detailed steps that you can use to prevent a control from running in
Internet Explorer, see <http://support.microsoft.com/kb/240797> Microsoft
Knowledge Base Article 240797. Follow these steps in this article to
create a Compatibility Flags value in the registry to prevent a COM object
from being instantiated in Internet Explorer.
To set the kill bits for CLSIDs with values of
{e5df9d10-3b52-11d1-83e8-00a0c90dc849} and
{844F4806-E8A8-11d2-9652-00C04FC30871}, paste the following text in a text
editor such as Notepad. Then, save the file by using the .reg file name
extension.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX
Compatibility\{e5df9d10-3b52-11d1-83e8-00a0c90dc849}]
"Compatibility Flags"=dword:00000400
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX
Compatibility\{844F4806-E8A8-11d2-9652-00C04FC30871}]
"Compatibility Flags"=dword:00000400
You can apply this .reg file to individual systems by double-clicking it.
You can also apply it across domains by using Group Policy. For more
information about Group Policy, visit the following Microsoft Web sites:
<http://support.microsoft.com/kb/240797> Group Policy Collection
<http://technet2.microsoft.com/WindowsServer/en/library/47ba1311-6cca-414f-98c9-2d7f99fca8a31033.mspx?mfr=true>
What is Group Policy Object Editor
<http://technet2.microsoft.com/WindowsServer/en/library/e926577a-5619-4912-b5d9-e73d4bdc94911033.mspx?mfr=true>
Core Group Policy Tools and Settings
Note You must restart Internet Explorer for your changes to take effect.
Note The compatibility flag for CLSID
{e5df9d10-3b52-11d1-83e8-00a0c90dc849} has an original DWORD value of
0x20000. If you deploy this workaround you should reset the DWORD value to
0x20000 rather than delete the key after you have installed the security
update. For more information of various values that determine the behavior
of registered Microsoft ActiveX controls see the following
<http://msdn.microsoft.com/library/default.asp?url=/workshop/components/com/reference/com_ref_entry.asp>
product documentation.
Impact of Workaround: Web sites that use the WebViewFolderIcon ActiveX
Control may no longer display or function correctly.
* Set Internet and Local Intranet security zone settings to High to
prompt before running ActiveX controls and Active Scripting in these
zones,
You can help protect against this vulnerability by changing your settings
for the Internet security zone to prompt before running ActiveX controls
and Active Scripting. You can do this by setting your security browser to
High.
To raise the browsing security level in Microsoft Internet Explorer,
follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then
click the Internet icon.
3.Under Security level for that zone, move the slider to High. This sets
the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the
slider to High.
Note Setting the level to High may cause some Web sites to work
incorrectly. If you have difficulty using a Web site after you change this
setting and you are sure the site is safe to use, you can add that site to
your list of trusted sites. This will allow the site to work correctly
even with the high security setting.
Impact of Workaround: There are side effects to prompting before running
ActiveX controls. Many Web sites that are on the Internet or on an
intranet use ActiveX to provide additional functionality. For example, an
online e-commerce site or banking site may use ActiveX controls to provide
menus, ordering forms, or even account statements. Prompting before
running ActiveX controls is a global setting that affects all Internet and
intranet sites. You will be prompted frequently when you enable this
workaround. For each prompt, if you feel you trust the site that you are
visiting, click Yes to run ActiveX controls. If you do not want to be
prompted for all these sites, use the Restrict Web sites to only your
trusted Web sites workaround.
* Configure Internet Explorer to prompt before running ActiveX controls
or disable ActiveX controls in the Internet and local intranet security
zone.
You can help protect against this vulnerability by changing your settings
to prompt before running ActiveX controls only. To do this, follow these
steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the ActiveX controls and plug-ins section, under Run
ActiveX controls and plug-ins, click Prompt.
5. In the Scripting section, under Active Scripting, click Prompt and then
click OK.
6. Click Local intranet and then click Custom Level.
7. Under Settings, in the ActiveX controls and plug-ins section, under Run
ActiveX controls and plug-ins, click Prompt.
8. In the Scripting section under Active Scripting, click Prompt.
9. Click OK two times to return to Internet Explorer.
Impact of Workaround: There are side effects to prompting before running
ActiveX controls. Many Web sites that are on the Internet or on an
intranet use ActiveX to provide additional functionality. For example, an
online e-commerce site or banking site may use ActiveX controls to provide
menus, ordering forms, or even account statements. Prompting before
running ActiveX controls is a global setting that affects all Internet and
intranet sites. You will be prompted frequently when you enable this
workaround. For each prompt, if you feel you trust the site that you are
visiting, click Yes to run ActiveX controls. If you do not want to be
prompted for all these sites, use the Restrict Web sites to only your
trusted Web sites workaround.
* Restrict Web sites to only your trusted Web sites
After you set Internet Explorer to require a prompt before it runs ActiveX
controls and Active Scripting in the Internet zone and in the Local
intranet zone, you can add sites that you trust to Internet Explorer s
Trusted sites zone. This will allow you to continue to use trusted Web
sites exactly as you do today, while helping to protect you from this
attack on untrusted sites. We recommend that you add only sites that you
trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click the Tools menu, click Internet Options, and
then click the Security tab.
2. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites and then click Sites.
3. If you want to add sites that do not require an encrypted channel,
click to clear the Require server verification (https:) for all sites in
this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that
you trust and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet
Explorer.
Add any sites that you trust not to take malicious action on your
computer. One in particular that you may want to add is
*.windowsupdate.microsoft.com (without the quotation marks). This is the
site that will host the update, and it requires an ActiveX control to
install the update.
FAQ for Windows Shell Remote Code Execution Vulnerability:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. 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.
What causes the vulnerability?
The vulnerability is caused by improper validation of input parameters to
the Windows Shell when invoked by the WebViewFolderIcon ActiveX object.
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?
While the vulnerability exists in Windows Explorer the attack vector is
exposed through the use of Internet Explorer. As a result, exploitation of
the vulnerability is through a Web-based attack scenario. In a Web-based
attack scenario, an attacker would have to host a Web site that contains a
Web page that is used to attempt to 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 persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's 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.
What systems are primarily at risk from the vulnerability?
Workstations and terminal servers 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.
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.
What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer 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 specially crafted Web
content on a server. Internet Explorer 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 correcting the parameter
validation done in the Windows Shell when invoked by the WebViewFolderIcon
ActiveX object.
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-2006-3730. It also has been
named WebViewFolderIcon setSlice by the larger security community. This
security bulletin addresses the publicly disclosed vulnerability.
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.
Does applying this security update help protect customers from the code
that has been published publicly that attempts to exploit this
vulnerability?
Yes. This security update addresses the vulnerability that is currently
being exploited. The vulnerability that has been addressed has been
assigned the Common Vulnerability and Exposure number CVE-2006-3730.
ADDITIONAL INFORMATION
The information has been provided by Microsoft Security Bulletin.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/ms06-057.mspx>
http://www.microsoft.com/technet/security/bulletin/ms06-057.mspx
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