Microsoft Security Bulletin MS09-043 - Critical Vulnerabilities in Microsoft Office Web Components Could Allow Remote Code Execution (957638)

Microsoft Security Bulletin MS09-043 - Critical
Vulnerabilities in Microsoft Office Web Components Could Allow Remote Code Execution (957638)
Published: August 11, 2009

Version: 1.0
General Information
Executive Summary

This security update resolves several privately reported vulnerabilities in Microsoft Office Web Components that could allow remote code execution if a user viewed a specially crafted Web page. An attacker who successfully exploited these vulnerabilities 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.

This security update is rated Critical for all supported editions of Microsoft Office XP, Microsoft Office 2003, Microsoft Office 2000 Web Components, Microsoft Office XP Web Components, Microsoft Office 2003 Web Components, Microsoft Office 2003 Web Components for the 2007 Microsoft Office system, Microsoft Internet Security and Acceleration Server 2004 Standard Edition, Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition, Microsoft Internet Security and Acceleration Server 2006, Microsoft BizTalk Server 2002, Microsoft Visual Studio .NET 2003, and Microsoft Office Small Business Accounting 2006. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses the vulnerabilities by correctly handling memory allocation when the ActiveX control is used in Internet Explorer, correcting validation logic for Office Web Components ActiveX control methods, and performing additional parameter validation. For more information about the vulnerabilities, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.

This security update also addresses the vulnerability first described in Microsoft Security Advisory 973472. The security updates addressed in this bulletin are not related to the vulnerabilities described in Microsoft Security Advisory 973882.

Recommendation. Microsoft recommends that customers apply the update immediately.

Known Issues. Microsoft Knowledge Base Article 957638 documents the currently known issues that customers may experience when installing this security update. The article also documents recommended solutions for these issues. When currently known issues and recommended solutions pertain only to specific releases of this software, this article provides links to further articles.
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Affected and Non-Affected Software

The following software have been tested to determine which versions or editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, visit Microsoft Support Lifecycle.

Affected Software
Office Suite and Other Software Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update
Microsoft Office Suites

Microsoft Office XP Service Pack 3
(KB947320)

Remote Code Execution

Critical

MS08-017

Microsoft Office 2003 Service Pack 3
(KB947319)

Remote Code Execution

Critical

None
Microsoft Office Web Components

Microsoft Office 2000 Web Components Service Pack 3
(KB947320)

Remote Code Execution

Critical

MS08-017

Microsoft Office XP Web Components Service Pack 3
(KB947320)

Remote Code Execution

Critical

MS08-017

Microsoft Office 2003 Web Components Service Pack 3
(KB947319)

Remote Code Execution

Critical

None

Microsoft Office 2003 Web Components Service Pack 1 for the 2007 Microsoft Office System**
(KB947318)

Remote Code Execution

Critical

None
Microsoft Internet Security and Acceleration Server

Microsoft Internet Security and Acceleration Server 2004 Standard Edition Service Pack 3*
(KB947826)

Remote Code Execution

Critical

None

Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition Service Pack 3
(KB947826)

Remote Code Execution

Critical

None

Microsoft Internet Security and Acceleration Server 2006 Standard Edition Service Pack 1
(KB947826)

Remote Code Execution

Critical

None

Microsoft Internet Security and Acceleration Server 2006 Enterprise Edition Service Pack 1
(KB947826)

Remote Code Execution

Critical

None
Other Microsoft Software

Microsoft BizTalk Server 2002
(KB971388)

Remote Code Execution

Critical

MS08-017

Microsoft Visual Studio .NET 2003 Service Pack 1
(KB969172)

Remote Code Execution

Critical

MS08-017

Microsoft Office Small Business Accounting 2006
(KB968377)

Remote Code Execution

Critical

None

*Microsoft ISA Server 2004 Standard Edition is delivered as a standalone product. Microsoft ISA Server 2004 Standard Edition is also delivered as a component of Windows Small Business Server 2003 Premium Edition Service Pack 1 and Windows Small Business Server 2003 R2 Premium Edition.

**SQL Server 2008 and Microsoft Forefront Threat Management Gateway Medium Business Edition redistribute the affected component Office 2003 Web Components for the 2007 Microsoft Office System. The update for the Office 2003 Web Components for the 2007 Microsoft Office System component detects for SQL Server 2008 and Microsoft Forefront Threat Management Gateway Medium Business Edition and will offer the update to customers.

Non-Affected Software
Office and Other Software

2007 Microsoft Office Suite Service Pack 1 and 2007 Microsoft Office Suite Service Pack 2

Microsoft Office 2004 for Mac

Microsoft Office 2008 for Mac

Microsoft Office PowerPoint Viewer 2003

Microsoft Office Word Viewer 2003

Microsoft Office Word Viewer 2003 Service Pack 3

Microsoft Office Excel Viewer 2003

Microsoft Office Excel Viewer 2003 Service Pack 3

Microsoft Office Excel Viewer

Microsoft Office PowerPoint 2007 Viewer

Microsoft Office PowerPoint Viewer 2007 Service Pack 1

Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Service Pack 1 and Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Service Pack 2

Microsoft Internet Security and Acceleration Server 2000 Service Pack 2*

Microsoft BizTalk Server 2004

Microsoft BizTalk Server 2006

Microsoft BizTalk Server 2009

Microsoft Visual Studio 2005

Microsoft Visual Studio 2005 Service Pack 1

Microsoft Visual Studio 2008

Microsoft Visual Studio 2008 Service Pack 1

Microsoft Visual Studio 2010

*Microsoft Internet Security and Acceleration Server 2000 Service Pack 2 is not-affected because the previous OWC release, MS08-017, set the kill bit needed to prevent this exploit.
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Frequently Asked Questions (FAQ) Related to This Security Update

How do I know which versions of OWC are still in support and which versions of Office they shipped with?
There are three versions of Office Web Components:
•

Office 2000 Web Components
•

Office XP Web Components
•

Office 2003 Web Components

Each version was released as a Web download and on the CDs of the corresponding version of Microsoft Office. In addition, each version was re-released together with the next version of Office. Therefore, there is a version of Office 2000 Web Components on the Office XP CDs and a version of Office XP Web Components on the Office 2003 CDs. The Office 2003 Web Components were not released on Office 2007 CDs. However, they were re-released to the Web and included with Microsoft Office Project Server 2007. Although these re-releases carry the same names and functionality as the original release, for technical reasons they are considered separate products for patching purposes.

Each version of OWC, and this includes the re-releases, is supported according to the version of Office with which it shipped. Therefore, the version of Office 2000 Web Components that shipped with Office 2000 was in extended support until Office 2000 left extended support on July 14, 2009. However, the version of Office 2000 Web Components that shipped with Office XP is in extended support until Office XP leaves extended support on July 12, 2011. This same rule applies to the other versions of OWC. The following table lists the support milestone dates and release locations for all the different versions of OWC:
OWC Version Release Location Mainstream Support Ends Extended Support Ends

OWC 2000 (Office 2000 version)

Office 2000 CD, Web

Mainstream support has ended.

Extended support has ended.

OWC 2000 (Office XP version)

Office XP CD

Mainstream support has ended.

7/12/2011

OWC XP (Office XP version)

Office XP CD, Web

Mainstream support has ended.

7/12/2011

OWC XP (Office 2003 version)

Office 2003 CD

Mainstream support has ended.

4/8/2014

OWC 2003 (Office 2003 version)

Office 2003 CD, Web (versions 1-3)

Mainstream support has ended.

4/8/2014

OWC 2003 (2007 Office system version)

Project Server 2007 CD, Web (version 4)

4/10/2012

4/11/2017

For more information about the support life cycle of Microsoft Office products, visit the Office Products Web site at Microsoft Help and Support.

Where are the file information details?
Refer to the reference tables in the Security Update Deployment section for the location of the file information details.

Why does this update address several reported security vulnerabilities?
This update contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files. Instead of having to install several updates that are almost the same, customers need to install this update only.

Does this update contain any security-related changes to functionality?
For affected versions of ISA Server, the update sets the kill bit for all OWC CLSIDs blocking known attack vectors within Internet Explorer. This action does not affect ISA Server functionality.

I am using an older release of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. To determine the support life cycle for your software release, visit Microsoft Support Lifecycle.

It should be a priority for customers who have older releases of the software to migrate to supported releases to prevent potential exposure to vulnerabilities. For more information about the Windows Product Lifecycle, visit Microsoft Support Lifecycle. For more information about the extended security update support period for these software versions or editions, visit Microsoft Product Support Services.

Customers who require custom support for older releases must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, visit Microsoft Worldwide Information, select the country, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager. For more information, see the Windows Operating System Product Support Lifecycle FAQ.
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Vulnerability Information

Severity Ratings and Vulnerability Identifiers

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the July bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Office Web Components Memory Allocation Vulnerability - CVE-2009-0562 Office Web Components Heap Corruption Vulnerability - CVE-2009-2496 Office Web Components HTML Script Vulnerability - CVE-2009-1136 Office Web Components Buffer Overflow Vulnerability - CVE-2009-1534 Aggregate Severity Rating
Microsoft Office Suites

Microsoft Office XP Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical

Microsoft Office 2003 Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical
Microsoft Office Web Components

Microsoft Office 2000 Web Components Service Pack 3

Not applicable

Not applicable

Not applicable

Critical
Remote Code Execution

Critical

Microsoft Office XP Web Components Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical

Microsoft Office 2003 Web Components Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical

Microsoft Office 2003 Web Components Service Pack 1 for the 2007 Microsoft Office System

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical
Microsoft Internet Security and Acceleration Server

Microsoft Internet Security and Acceleration Server 2004 Standard Edition Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical

Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition Service Pack 3

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical

Microsoft Internet Security and Acceleration Server 2006 Standard Edition Service Pack 1

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical

Microsoft Internet Security and Acceleration Server 2006 Enterprise Edition Service Pack 1

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical
Other Microsoft Software

Microsoft BizTalk Server 2002

Not applicable

Not applicable

Not applicable

Critical
Remote Code Execution

Critical

Microsoft Visual Studio .NET 2003 Service Pack 1

Not applicable

Not applicable

Not applicable

Critical
Remote Code Execution

Critical

Microsoft Office Small Business Accounting 2006

Critical
Remote Code Execution

Critical
Remote Code Execution

Critical
Remote Code Execution

Not applicable

Critical
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Office Web Components Memory Allocation Vulnerability - CVE-2009-0562

A remote code execution vulnerability exists in the Office Web Components ActiveX Control. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-0562.

Mitigating Factors for Office Web Components Memory Allocation Vulnerability - CVE-2009-0562

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:
•

By default, Internet Explorer on Windows Server 2003 and 2008 runs in a restricted mode that is known as 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.
•

By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally, Outlook 2000 opens HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.

The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
•

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.
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Workarounds for Office Web Components Memory Allocation Vulnerability - CVE-2009-0562

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:
•

Prevent Office Web Components Library from running in Internet Explorer.

You can prevent the Office Web Components Library from running 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.

Note This is the action taken by the ISA Server update package. No binaries are included in this update for ISA Server.

For detailed steps that you can use to prevent a control from running in Office Web Components, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent the Office Web Components library from running.

Note The Class Identifiers and corresponding files where the library objects are contained are documented in the FAQ "What does the update do?"
•

To set the kill bit for a CLSID with a value of {0002E543-0000-0000-C000-000000000046} and {0002E55B-0000-0000-C000-000000000046}, 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\{0002E543-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E55B-0000-0000-C000-000000000046}]
"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: Disabling the Office Web Component prevents Internet Explorer from instantiating the control. This configuration causes program compatibility issues when Office Web Components functionality is required.

How to undo the Workaround: You can undo the workaround documented above by following these steps:

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

To undo the kill bit for a CLSID with a value of {0002E543-0000-0000-C000-000000000046} and {0002E55B-0000-0000-C000-000000000046}, 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

CLSID_OWC10_Spreadsheet, {0002E541-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E543-0000-0000-C000-000000000046}]

CLSID_OWC11_Spreadsheet, {0002E559-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E55B-0000-0000-C000-000000000046}]
•

Unregister the Office Web Components Library

Note This action will not work on an ISA Server computer because:
•

The Office Web components are installed in the ISA Server program directory (“%ProgramFiles%\Microsoft ISA Server” by default)
•

The Office Web Components are re-registered by the ISA Server report job mechanism each time a report job is executed.

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"

Impact of Workaround: Applications requiring Office Web Components functionality will not function.

How to undo the Workaround: To re-register the Office Web Components, follow these steps:
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"
•

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:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

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.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

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. Two in particular that you may want to add are ".windowsupdate.microsoft.com" and ".update.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.
•

Set Internet and Local intranet security zone settings to "High" to prompt before running ActiveX controls in these zones

You can help protect against these vulnerabilities by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

Under Security level for this 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 security setting set to High.
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FAQ for Office Web Components Memory Allocation Vulnerability - CVE-2009-0562

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. 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 the ActiveX control is used in Internet Explorer, the control may corrupt the system state in such a way that an attacker could run arbitrary code.

What are Office Web Components?
Microsoft Office Web Components are a collection of Component Object Model (COM) controls for publishing spreadsheets, charts, and databases to the Web, and for viewing the published components on the Web.

What might an attacker use the vulnerability to do?
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?
An attacker could exploit the vulnerability by hosting a specially crafted Web site that is designed to invoke the ActiveX control through Internet Explorer. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. These Web sites 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 convince 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.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit 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. 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 for Windows Server 2003 or Windows Server 2008. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

What does the update do?
The update removes the vulnerability by correctly handling memory allocation when the ActiveX control is used in Internet Explorer.

For affected versions of ISA Server, the update sets the kill bit for all OWC CLSIDs blocking known attack vectors within Internet Explorer. This action does not affect ISA Server functionality.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

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.
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Office Web Components Heap Corruption Vulnerability - CVE-2009-2496

A remote code execution vulnerability exists in the Office Web Components ActiveX Control. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-2496.

Mitigating Factors for Office Web Components Heap Corruption Vulnerability - CVE-2009-2496

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:
•

By default, Internet Explorer on Windows Server 2003 and 2008 runs in a restricted mode that is known as 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.
•

By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.

The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
•

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.
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Workarounds for Office Web Components Heap Corruption Vulnerability - CVE-2009-2496

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:
•

Prevent Office Web Components Library from running in Internet Explorer.

You can prevent the Office Web Components Library from running 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.

Note This is the action taken by the ISA Server update package. No binaries are included in this update for ISA Server.

For detailed steps that you can use to prevent a control from running in Office Web Components, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent the Office Web Components library from running.

Note The Class Identifiers and corresponding files where the library objects are contained are documented in the FAQ "What does the update do?"
•

To set the kill bit for a CLSID with a value of {0002E541-0000-0000-C000-000000000046} and {0002E559-0000-0000-C000-000000000046}, 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\{0002E541-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E559-0000-0000-C000-000000000046}]
"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: Disabling the Office Web Component prevents Internet Explorer from instantiating the control. This configuration causes program compatibility issues when Office Web Components functionality is required.

How to undo the Workaround: You can undo the workaround documented above by following these steps:

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

To undo the kill bit for a CLSID with a value of {0002E541-0000-0000-C000-000000000046} and {0002E559-0000-0000-C000-000000000046}, 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

CLSID_OWC10_Spreadsheet, {0002E541-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E541-0000-0000-C000-000000000046}]

CLSID_OWC11_Spreadsheet, {0002E559-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E559-0000-0000-C000-000000000046}]
•

Unregister the Office Web Components Library

Note This action will not work on an ISA Server computer because:
•

The Office Web components are installed in the ISA Server program directory (“%ProgramFiles%\Microsoft ISA Server” by default)
•

The Office Web Components are re-registered by the ISA Server report job mechanism each time a report job is executed.

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"

Impact of Workaround: Applications requiring Office Web Components functionality will not function.

How to undo the Workaround: To re-register the Office Web Components, follow these steps:
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"
•

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:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

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.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

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. Two in particular that you may want to add are ".windowsupdate.microsoft.com" and ".update.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.
•

Set Internet and Local intranet security zone settings to "High" to prompt before running ActiveX controls in these zones

You can help protect against these vulnerabilities by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

Under Security level for this 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 security setting set to High.
Top of sectionTop of section

FAQ for Office Web Components Heap Corruption Vulnerability - CVE-2009-2496

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. 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 the ActiveX control is used in Internet Explorer, the control methods do not perform sufficient parameter validation which may result in a heap overflow in such a way that an attacker could run arbitrary code.

What are Office Web Components?
Microsoft Office Web Components are a collection of Component Object Model (COM) controls for publishing spreadsheets, charts, and databases to the Web, and for viewing the published components on the Web.

What might an attacker use the vulnerability to do?
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?
An attacker could exploit the vulnerability by hosting a specially crafted Web site that is designed to invoke the ActiveX control through Internet Explorer. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. These Web sites 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 convince 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.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit 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. 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 for Windows Server 2003 or Windows Server 2008. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

What does the update do?
The update removes the vulnerability by correcting validation logic for Office Web Components ActiveX control methods.

For affected versions of ISA Server, the update sets the kill bit for all OWC CLSIDs blocking known attack vectors within Internet Explorer.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

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.
Top of sectionTop of section
Top of sectionTop of section

Office Web Components HTML Script Vulnerability - CVE-2009-1136

A remote code execution vulnerability exists in the Office Web Components ActiveX Control. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1136.

Mitigating Factors for Office Web Components HTML Script Vulnerability - CVE-2009-1136

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:
•

By default, Internet Explorer on Windows Server 2003 and 2008 runs in a restricted mode that is known as 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.
•

By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.

The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
•

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.
Top of sectionTop of section

Workarounds for Office Web Components HTML Script Vulnerability - CVE-2009-1136

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:
•

Prevent Office Web Components Library from running in Internet Explorer.

You can prevent the Office Web Components Library from running 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.

Note This is the action taken by the ISA Server update package. No binaries are included in this update for ISA Server.

For detailed steps that you can use to prevent a control from running in Office Web Components, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent the Office Web Components library from running.

Note The Class Identifiers and corresponding files where the library objects are contained are documented in the FAQ "What does the update do?"
•

To set the kill bit for a CLSID with a value of {0002E541-0000-0000-C000-000000000046} and {0002E559-0000-0000-C000-000000000046}, 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\{0002E541-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E559-0000-0000-C000-000000000046}]
"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: Disabling the Office Web Component prevents Internet Explorer from instantiating the control. This configuration causes program compatibility issues when Office Web Components functionality is required.

How to undo the Workaround: You can undo the workaround documented above by following these steps:

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

To undo the kill bit for a CLSID with a value of {0002E541-0000-0000-C000-000000000046} and {0002E559-0000-0000-C000-000000000046}, 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

CLSID_OWC10_Spreadsheet, {0002E541-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E541-0000-0000-C000-000000000046}]

CLSID_OWC11_Spreadsheet, {0002E559-0000-0000-C000-000000000046}[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E559-0000-0000-C000-000000000046}]
•

Unregister the Office Web Components Library

Note This action will not work on an ISA Server computer because:
•

The Office Web components are installed in the ISA Server program directory (“%ProgramFiles%\Microsoft ISA Server” by default)
•

The Office Web Components are re-registered by the ISA Server report job mechanism each time a report job is executed.

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"

Impact of Workaround: Applications requiring Office Web Components functionality will not function.

How to undo the Workaround: To re-register the Office Web Components, follow these steps:
•

For OWC 10, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\10\owc10.dll"
•

For OWC 11, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Common Files\Microsoft Shared\Web Components\11\owc11.dll"
•

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:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

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.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

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. Two in particular that you may want to add are ".windowsupdate.microsoft.com" and ".update.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.
•

Set Internet and Local intranet security zone settings to "High" to prompt before running ActiveX controls in these zones

You can help protect against these vulnerabilities by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

Under Security level for this 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 security setting set to High.
Top of sectionTop of section

FAQ for Office Web Components HTML Script Vulnerability - CVE-2009-1136

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. 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 the ActiveX control is used in Internet Explorer, the control does not correctly handle parameter values and may corrupt the system state in such a way that an attacker could run arbitrary code.

What are Office Web Components?
Microsoft Office Web Components are a collection of Component Object Model (COM) controls for publishing spreadsheets, charts, and databases to the Web, and for viewing the published components on the Web.

What might an attacker use the vulnerability to do?
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?
An attacker could exploit the vulnerability by hosting a specially crafted Web site that is designed to invoke the ActiveX control through Internet Explorer. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. These Web sites 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 convince 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.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit 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. 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 for Windows Server 2003 or Windows Server 2008. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

What does the update do?
The security update addresses the vulnerability by performing additional parameter validation.

For affected versions of ISA Server, the update sets the kill bit for all OWC CLSIDs blocking known attack vectors within Internet Explorer. This action does not affect ISA Server functionality.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
While the initial report was provided through responsible disclosure, the vulnerability was later disclosed publicly by a separate party. This security bulletin addresses the publicly disclosed vulnerability, as well as additional issues discovered through internal investigations. This vulnerability was first described in Microsoft Security Advisory 973472.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
Yes. Microsoft is aware of limited, targeted attacks attempting to exploit the vulnerability.
Top of sectionTop of section
Top of sectionTop of section

Office Web Components Buffer Overflow Vulnerability - CVE-2009-1534

A remote code execution vulnerability exists in the Office Web Components ActiveX Control. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1534.

Mitigating Factors for Office Web Components Buffer Overflow Vulnerability - CVE-2009-1534

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:
•

By default, Internet Explorer on Windows Server 2003 and 2008 runs in a restricted mode that is known as 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.
•

By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally, Outlook 98 and Outlook 2000 open HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.

The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
•

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.
Top of sectionTop of section

Workarounds for Office Web Components Buffer Overflow Vulnerability - CVE-2009-1534

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:
•

Prevent Office Web Components Library from running in Internet Explorer.

You can prevent the Office Web Components Library from running 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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.

Note This is the action taken by the ISA Server update package. No binaries are included in this update for ISA Server.

For detailed steps that you can use to prevent a control from running in Office Web Components, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent the Office Web Components library from running.

Note The Class Identifiers and corresponding files where the library objects are contained are documented in the FAQ "What does the update do?"
•

To set the kill bit for a CLSID with a value of {0002E512-0000-0000-C000-000000000046}, 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\{0002E512-0000-0000-C000-000000000046}]
"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: Disabling the Office Web Component prevents Internet Explorer from instantiating the control. This configuration causes program compatibility issues when Office Web Components functionality is required.

How to undo the Workaround: You can undo the workaround documented above by following these steps:

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

To undo the kill bit for a CLSID with a value of {0002E512-0000-0000-C000-000000000046}, 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\{0002E512-0000-0000-C000-000000000046}]
•

Unregister the Office Web Components Library

Note This action will not work on an ISA Server computer because:
•

The Office Web components are installed in the ISA Server program directory (“%ProgramFiles%\Microsoft ISA Server” by default)
•

The Office Web Components are re-registered by the ISA Server report job mechanism each time a report job is executed.

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 the Registry Editor at your own risk. For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe.

Note We recommend backing up the registry before you edit it.
•

For Office 2000, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Microsoft Office\Office\msowc.dll"
•

For Office XP, type the following at the command prompt and select Run:

Regsvr32.exe /u "C:\Program Files\Microsoft Office\Office10\msowc.dll"

Impact of Workaround: Applications requiring Office Web Components functionality will not function.

How to undo the Workaround: To re-register the Office Web Components, follow these steps:
•

For Office 2000, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Microsoft Office\Office\msowc.dll"
•

For Office XP, type the following at the command prompt and select Run:

Regsvr32.exe "C:\Program Files\Microsoft Office\Office10\msowc.dll
•

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:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

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.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

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. Two in particular that you may want to add are ".windowsupdate.microsoft.com" and ".update.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.
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Set Internet and Local intranet security zone settings to "High" to prompt before running ActiveX controls in these zones

You can help protect against these vulnerabilities by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

Under Security level for this 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 security setting set to High.
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FAQ for Office Web Components Buffer Overflow Vulnerability - CVE-2009-1534

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. 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 the ActiveX control is used in Internet Explorer, the control may corrupt the system state in such a way that an attacker could run arbitrary code.

What are Office Web Components?
Microsoft Office Web Components are a collection of Component Object Model (COM) controls for publishing spreadsheets, charts, and databases to the Web, and for viewing the published components on the Web.

What might an attacker use the vulnerability to do?
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?
An attacker could exploit the vulnerability by hosting a specially crafted Web site that is designed to invoke the ActiveX control through Internet Explorer. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. These Web sites 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 convince 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.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit 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. 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 for Windows Server 2003 or Windows Server 2008. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

What does the update do?
The update removes the vulnerability by validating property values with boundary checks when the ActiveX control is used in Internet Explorer.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

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.

Other Information
Acknowledgments

Microsoft thanks the following for working with us to help protect customers:
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Peter Vreugdenhil of Zero Day Initiative for reporting the Office Web Components Memory Allocation Vulnerability (CVE-2009-0562).
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Peter Vreugdenhil of Zero Day Initiative for reporting the Office Web Components Heap Corruption Vulnerability (CVE-2009-2496).
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Peter Vreugdenhil of Zero Day Initiative and Haifei Li of Fortinet’s FortiGuard Global Security Research Team for reporting the Office Web Components HTML Script Vulnerability (CVE-2009-1136).
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Sean Larsson of VeriSign iDefense Labs for reporting the Office Web Components Buffer Overflow Vulnerability (CVE-2009-1534).

Microsoft Active Protections Program (MAPP)

To improve security protections for customers, Microsoft provides vulnerability information to major security software providers in advance of each monthly security update release. Security software providers can then use this vulnerability information to provide updated protections to customers via their security software or devices, such as antivirus, network-based intrusion detection systems, or host-based intrusion prevention systems. To determine whether active protections are available from security software providers, please visit the active protections Web sites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.

Support
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Customers in the U.S. and Canada can receive technical support from Security Support or 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates. For more information about available support options, see Microsoft Help and Support.
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International customers can receive support from their local Microsoft subsidiaries. There is no charge for support that is associated with security updates. For more information about how to contact Microsoft for support issues, visit the International Support Web site.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions
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V1.0 (August 11, 2009): Bulletin published.