Microsoft Security Advisory (953839)

Purpose of Advisory: Notification of the availability of an update of ActiveX kill bits.

Advisory Status: Microsoft Knowledge Base Article and associated update were released.

Recommendation: Review the referenced Knowledge Base Article and apply the appropriate update.

This advisory discusses the following software.

Does this update replace the Cumulative Security Update of ActiveX Kill Bits (950760)?
No, for the purpose of automatic updating, this update does not replace the Cumulative Security Update of ActiveX Kill Bits (950760) that is described in Microsoft Security Bulletin MS08-032. Automatic updating will still offer the MS08-032 update to customers regardless of whether or not they installed this update (953839). However, customers who install this update (953839) do not need to install the MS08-032 update to be protected with all the kill bits set in MS08-032.

Do users with a Windows Server 2008 Server Core installation need to install this update?
Users with a Windows Server 2008 Server Core installation will be offered this update, but do not need to install it. For more information on the Server Core installation option, see Server Core. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008; see Compare Server Core Installation Options.

Why is Microsoft releasing this Update Rollup for ActiveX Kill Bits with a security advisory when previous kill bit updates were released with a security bulletin?
Microsoft is releasing this Update Rollup for ActiveX Kill Bits with an advisory because the new kill bits do not affect Microsoft software.

Why does this advisory not have a security rating associated with it?
This update contains kill bits for third-party controls not owned by Microsoft. Microsoft does not provide a security rating for vulnerable third-party controls.

Does this update contain kill bits that were previously released in a Cumulative Security Update of ActiveX Kill Bits?
Yes, this update also includes kill bits that were previously set in Microsoft Security Bulletin MS08-032.

Does this update contain kill bits that were previously shipped in an Internet Explorer security update?
No, this update does not include kill bits that were previously shipped in an Internet Explorer security update. We recommend that you install the latest Cumulative Security Update for Internet Explorer.

What is a kill bit?
A security feature in Microsoft Internet Explorer makes it possible to prevent an ActiveX control from ever being loaded by the Internet Explorer HTML-rendering engine. This is done by making a registry setting and is referred to as setting the kill bit. After the kill bit is set, the control can never be loaded, even when it is fully installed. Setting the kill bit makes sure that even if a vulnerable component is introduced or is re-introduced to a system, it remains inert and harmless.

For more information, see Microsoft Knowledge Base Article 240797: How to stop an ActiveX control from running in Internet Explorer.

What is a security update of ActiveX kill bits? 
This security update only contains the class IDs (CLSID) of certain ActiveX controls that are the basis of this security update.

Why does this update not contain any binary files?
This update only makes changes to the registry to disable the control from instantiating in Internet Explorer.

Should I install this update if I do not have the affected component installed or use the affected platform?
Yes. Installing this update will block the vulnerable control from running in Internet Explorer.

Do I need to reapply this update if I install an ActiveX control discussed in this security update at a later date?
No, reapplying this update is not required. The kill bit will block Internet Explorer from running the control even if the control is installed at a later date.

What does this update do?
This update sets the kill bit for a list of Class Identifiers (CLSIDs).

The following Class Identifiers relate to a request by Aurigma to kill bit a list of Class Identifiers that are vulnerable. Further details can be found in the advisory issued by Aurigma:

The following Class Identifiers relate to a request by HP to kill bit a list of Class Identifiers that are vulnerable. Further details can be found in the advisories (c01422264) and (c01439758) issued by HP:

Review the Microsoft Knowledge Base Article that is associated with this advisory

Microsoft encourages customers to install this update. Customers who are interested in learning more about this update should review Microsoft Knowledge Base Article 953839.

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:

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Prevent COM objects from running in Internet Explorer You can disable attempts to instantiate a COM object 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 Microsoft Knowledge Base Article 240797. Follow the steps in this article to create a Compatibility Flags value in the registry to prevent a COM object from being instantiated in Internet Explorer. Note The Class Identifiers and corresponding files where the ActiveX objects are contained are documented under "What does this update do?" in the FAQ section above. Replace {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the Class Identifiers found in this section. To set the kill bit for a CLSID with a value of {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}, 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\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }] "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: • Group Policy collection • What is Group Policy Object Editor? • Core Group Policy tools and settings Note You must restart Internet Explorer for your changes to take effect. Impact of Workaround: There is no impact as long as the object is not intended to be used in Internet Explorer.

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