Microsoft Security Bulletin MS10-022 - Important Vulnerability in VBScript Scripting Engine Could Allow Remote Code Execution (981169)

Microsoft Security Bulletin MS10-022 - Important
Vulnerability in VBScript Scripting Engine Could Allow Remote Code Execution (981169)
Published: April 13, 2010

Version: 1.0
General Information
Executive Summary

This security update resolves a publicly disclosed vulnerability in VBScript on Microsoft Windows that could allow remote code execution. This security update is rated Important for Microsoft Windows 2000, Windows XP, and Windows Server 2003. On Windows Server 2008, Windows Vista, Windows 7, and Windows Server 2008 R2, the vulnerable code is not exploitable, however, as the code is present, this update is provided as a defense-in-depth measure and has no severity rating. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The vulnerability could allow remote code execution if a malicious Web site displayed a specially crafted dialog box on a Web page and a user pressed the F1 key, causing the Windows Help System to be started with a Windows Help File provided by the attacker. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system.

The security update addresses the vulnerability by modifying the way that the VBScript engine processes help files in protected mode. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.

This security update addresses the vulnerability first described in Microsoft Security Advisory 981169.

Recommendation. The majority of customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.

For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update at the earliest opportunity using update management software, or by checking for updates using the Microsoft Update service.

See also the section, Detection and Deployment Tools and Guidance, later in this bulletin.

Known Issues. Microsoft Knowledge Base Article 981169 documents the currently known issues that customers may experience when installing this security update. The article also documents recommended solutions for these issues.
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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
Operating System Component Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update
Microsoft Windows 2000

Microsoft Windows 2000 Service Pack 4

VBScript 5.1[1]
(KB981350)

VBScript 5.6
(KB981350)

VBScript 5.7
(KB981349)

Remote Code Execution

Important

None
Windows XP

Windows XP Service Pack 2

VBScript 5.6
(KB981350)

Remote Code Execution

Important

None

Windows XP Service Pack 2 and Windows XP Service Pack 3

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

Remote Code Execution

Important

None

Windows XP Professional x64 Edition Service Pack 2

VBScript 5.6
(KB981350)

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

Remote Code Execution

Important

None
Windows Server 2003

Windows Server 2003 Service Pack 2

VBScript 5.6
(KB981350)

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

Remote Code Execution

Important

None

Windows Server 2003 x64 Edition Service Pack 2

VBScript 5.6
(KB981350)

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

Remote Code Execution

Important

None

Windows Server 2003 with SP2 for Itanium-based Systems

VBScript 5.6
(KB981350)

VBScript 5.7
(KB981349)

Remote Code Execution

Important

None
Windows Vista

Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

None

None[2]

None

Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

None

None[2]

None
Windows Server 2008

Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2**

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

None

None[2]

None

Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2**

VBScript 5.7
(KB981349)

VBScript 5.8
(KB981332)

None

None[2]

None

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

VBScript 5.7
(KB981349)

None

None[2]

None
Windows 7

Windows 7 for 32-bit Systems

VBScript 5.8
(KB981332)

None

None[2]

None

Windows 7 for x64-based Systems

VBScript 5.8
(KB981332)

None

None[2]

None
Windows Server 2008 R2

Windows Server 2008 R2 for x64-based Systems**

VBScript 5.8
(KB981332)

None

None[2]

None

Windows Server 2008 R2 for Itanium-based Systems

VBScript 5.8
(KB981332)

None

None[2]

None

**Server Core installation not affected. The vulnerability addressed by this update does not affect supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, when installed using the Server Core installation option. For more information on this installation option, see the MSDN articles, Server Core and Server Core for Windows Server 2008 R2. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options.

[1]This security update upgrades your installation of VBScript 5.1 to VBScript 5.6.

[2]Severity ratings do not apply to this update because the vulnerability discussed in this bulletin does not affect this software. However, as a defense-in-depth measure to protect against any possible new vectors identified in the future, Microsoft recommends that customers of this software apply this security update.
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Frequently Asked Questions (FAQ) Related to This Security Update

What version of VBScript is installed on my system?
The version of VBScript on a system is determined by the highest version included in Internet Explorer, the Windows operating system, or Windows Scripting Host that is installed on the system, and may change if a newer version of Microsoft Internet Explorer, Windows Service Pack or Windows Scripting Host is installed. For more information, see the MSDN article, VBScript Version Information.

To determine which version of VBScript is on your system, perform the following steps:

Open Windows Explorer.

Navigate to the %systemroot%\system32 directory.

Right-click on vbscript.dll, select Properties, and then click the Details tab.

The version number will be listed in the File Version field. For example, if your file version starts with 5.8, for example 5.8.7600.16385, VBScript 5.8 is installed on your system.

I am using VBScript 5.1. Is my system affected?
Yes, security update KB981350 applies to your system and will upgrade your version of VBScript to VBScript 5.6. See Microsoft Knowledge Base Article 981350 for more information about this update.

Note VBScript 5.1 is only present on new installations of Microsoft Windows 2000 Service Pack 4 that do not yet have Internet Explorer 6 installed. On such a system, installing the security update will upgrade your version of VBScript to VBScript 5.6.

I am using Windows Vista, Windows Server 2008, Windows 7, or Windows Server 2008 R2. Why am I receiving this update?
The vulnerability exists in a Windows file, vbscript.dll, that is included in supported editions of Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2. Microsoft has not identified any way to exploit this vulnerability on computers using these operating systems. As a defense-in-depth measure, this security update is made available to all customers using supported editions of Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2.

If I applied workarounds provided in Advisory 981169, do I need to reverse them before applying this update?
If you applied workarounds provided in Microsoft Security Advisory 981169, you do not need to undo them before you install this update. If you wish to undo the workarounds, it is safe to do so after installing the update. The advisory uses the workarounds recommended in this bulletin. Please review the corresponding Impact of Workaround information to learn more about what happens if you keep the workaround in place.

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.

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. For more information about the product lifecycle, visit the Microsoft Support Lifecycle Web site.

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. To determine the support lifecycle for your software release, see Select a Product for Lifecycle Information. For more information about service packs for these software releases, see Lifecycle Supported Service Packs.

Customers who require custom support for older software 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 the Microsoft Worldwide Information Web site, select the country in the Contact Information list, 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 Microsoft Support Lifecycle Policy 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 April bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software VBScript Help Keypress Vulnerability - CVE-2010-0483 Aggregate Severity Rating
VBScript 5.1

VBScript 5.1 on Microsoft Windows 2000 Service Pack 4[1]

Important
Remote Code Execution

Important
VBScript 5.6

VBScript 5.6 on Microsoft Windows 2000 Service Pack 4

Important
Remote Code Execution

Important

VBScript 5.6 on Windows XP Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.6 on Windows XP Professional x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.6 on Windows Server 2003 Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.6 on Windows Server 2003 x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.6 on Windows Server 2003 with SP2 for Itanium-based Systems

Important
Remote Code Execution

Important
VBScript 5.7

VBScript 5.7 on Microsoft Windows 2000 Service Pack 4

Important
Remote Code Execution

Important

VBScript 5.7 on Windows XP Service Pack 2 and Windows XP Service Pack 3

Important
Remote Code Execution

Important

VBScript 5.7 on Windows XP Professional x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.7 on Windows Server 2003 Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.7 on Windows Server 2003 x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.7 on Windows Server 2003 with SP2 for Itanium-based Systems

Important
Remote Code Execution

Important

VBScript 5.7 on Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 3

None[2]

None

VBScript 5.7 on Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

None[2]

None

VBScript 5.7 on Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2**

None[2]

None

VBScript 5.7 on Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2**

None[2]

None
VBScript 5.8

VBScript 5.8 on Windows XP Service Pack 2 and Windows XP Service Pack 3

Important
Remote Code Execution

Important

VBScript 5.8 on Windows XP Professional x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.8 on Windows Server 2003 Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.8 on Windows Server 2003 x64 Edition Service Pack 2

Important
Remote Code Execution

Important

VBScript 5.8 on Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 3

None[2]

None

VBScript 5.8 on Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

None[2]

None

VBScript 5.8 on Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2**

None[2]

None

VBScript 5.8 on Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2**

None[2]

None

VBScript 5.8 on Windows 7 for 32-bit Systems

None[2]

None

VBScript 5.8 on Windows 7 for x64-based Systems

None[2]

None

VBScript 5.8 on Windows Server 2008 R2 for x64-based Systems**

None[2]

None

VBScript 5.8 on Windows Server 2008 R2 for Itanium-based Systems

None[2]

None

**Server Core installation not affected. The vulnerability addressed by this update does not affect supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, when installed using the Server Core installation option. For more information on this installation option, see the MSDN articles, Server Core and Server Core for Windows Server 2008 R2. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options.

[1]This security update replaces your installation of VBScript 5.1 with VBScript 5.6.

[2]Severity ratings do not apply to this update because the vulnerability discussed in this bulletin does not affect this software. However, as a defense-in-depth measure to protect against any possible new vectors identified in the future, Microsoft recommends that customers of this software apply this security update.
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VBScript Help Keypress Vulnerability - CVE-2010-0483

A remote code execution vulnerability exists in the way that VBScript interacts with Windows Help files when using Internet Explorer. If a malicious Web site displayed a specially crafted dialog box and a user pressed the F1 key, the Windows Help System would be started with a Windows Help File provided by the attacker. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. On systems running Windows Server 2003, Internet Explorer Enhanced Security Configuration is enabled by default, which helps to mitigate against this issue.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-0483.

Mitigating Factors for VBScript Help Keypress Vulnerability - CVE-2010-0483

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:
•

This vulnerability cannot be exploited on Windows Vista, Windows Server 2008, Windows 7, or Windows Server 2008 R2.
•

This vulnerability requires user interaction. The vulnerability could not be exploited without user interaction even if the user visited a malicious Web site. Instead, an attacker would need to convince a user to press the F1 key on the keyboard while the Web site displays a scripted dialog box.
•

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 convince 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.
•

By default, all supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML e-mail messages in the Restricted sites zone, removing the risk of an attacker being able to use this vulnerability to execute malicious code. The Restricted sites zone helps mitigate attacks that could try to exploit this vulnerability by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, the user could still be vulnerable to exploitation of this vulnerability through the Web-based attack scenario. Additionally, Outlook 2007 uses a different component to render HTML e-mail, removing the risk of this exploit.
•

By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone.
•

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 affected than users who operate with administrative user rights.
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Workarounds for VBScript Help Keypress Vulnerability - CVE-2010-0483

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:
•

Do not press the F1 key when prompted by a Web site

Successful exploitation of this vulnerability requires that users assist the exploit by pressing the F1 key on their keyboard. Our analysis shows that if users do not press the F1 key on their keyboard, the vulnerability cannot be exploited.

Consequently, malicious Web sites may attempt to convince users to press the F1 key. Such a Web site could invoke an endless loop of dialog boxes that tell the user to press the F1 key to end the loop, or offer information such as pricing information or help to be revealed through the F1 key.

Users are advised to avoid pressing F1 presented by Web pages or other Internet content. If a dialog box appears repeatedly in an attempt to convince the user to press F1, users may log off the system or use Task Manager to terminate the Internet Explorer process.
•

Restrict access to the Windows Help System

Successful exploitation of this vulnerability requires that the Windows Help System is functioning. You can help protect against exploitation of this vulnerability if you modify the ACL on winhlp32.exe to be more restrictive on Windows 2000, Windows XP, and Windows Server 2003 by running the following command from an administrative command line:

echo Y | cacls "%windir%\winhlp32.exe" /E /P everyone:N

Note You must be logged in as administrator or have administrative credentials to complete this workaround.

Impact of workaround. The Windows Help System will be unavailable, and users may not be able to invoke the help function in applications. The attempt to open the Help function in applications may lead to an error message.

How to undo the workaround.

Run the following command from an administrative command line:

echo Y | cacls "%windir%\winhlp32.exe" /E /P everyone

Note You must be logged in as administrator or have administrative credentials to undo this workaround.
•

Set Internet and Local intranet security zone settings to "High" to block ActiveX Controls and Active Scripting in these zones

You can help protect against exploitation of this vulnerability by changing your settings for the Internet security zone to block ActiveX controls and Active Scripting. You can do this by setting your browser security to High.

To raise the browsing security level in 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.

Impact of workaround. There are side effects to blocking ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting 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. Blocking ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. If you do not want to block ActiveX Controls or Active Scripting for such sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone".

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to block ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect yourself 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.

Note Add any sites that you trust not to take malicious action on your system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.
•

Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone

You can help protect against exploitation of this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:

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

Click Internet, and then click Custom Level.

Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

Click Local intranet, and then click Custom Level.

Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

Click OK two times to accept the changes and return to Internet Explorer.

Note Disabling Active Scripting in the Internet and Local intranet security zones 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.

Impact of workaround. There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting 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 Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone".

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to block ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect yourself 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.

Note Add any sites that you trust not to take malicious action on your system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.
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FAQ for VBScript Help Keypress Vulnerability - CVE-2010-0483

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 logged-on 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 exists in the way that VBScript interacts with Windows Help files when using Internet Explorer. While Windows Help Files are inherently unsafe files, the implementation of VBScript on affected systems allows an attacker to specify a Help file location when displaying a dialog box on a Web page. If a visitor pressed the F1 key while such a dialog box is being displayed, this specially crafted Help file could be loaded by the Windows Help System, allowing execution of arbitrary code in the security context of the currently logged-on user.

What is VBScript?
VBScript (Visual Basic Script) is an interpreted, object-based scripting language that is often used to make Web sites more flexible or interactive. VBScript scripts can run only in the presence of an interpreter or host, such as Active Server Pages (ASP), Internet Explorer, or Windows Script Host. For more information, see the MSDN article VBScript Fundamentals.

What are unsafe file types?
Microsoft uses the concept of "unsafe file types" to help better protect users from executable content that an attacker could embed in such files. For more information, see the whitepaper Understanding Executable Content in Microsoft Products, and Microsoft Knowledge Base Article 291369.

What is the F1 key?
F1 is one of the 12 function keys (F1 – F12) on a regular keyboard, typically located in the top row of keys. Function keys allow users to reach certain functions in an application by pressing only a single key on the keyboard. In most applications, F1 would bring up the Help function and many users are familiar with instructions such as "Press F1 for help".

What is defense-in-depth?
In information security, defense-in-depth refers to an approach in which multiple layers of defense are in place to help prevent attackers from compromising the security of a network or system.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run arbitrary code as the logged-on user. If a user is logged on with administrative user rights, an attacker could take complete control of the affected system.

How could an attacker exploit the vulnerability?
Successful exploitation of this vulnerability requires that an attacker convince a user to visit a specially crafted Web page that displays a dialog box, and then convince the user to press the F1 key on the keyboard while this dialog box is being displayed.

What systems are primarily at risk from the vulnerability?
Client, workstation, or terminal server systems where Internet Explorer is used to browse Web pages are primarily at risk.

I am running Internet Explorer on Windows Server 2003 or Windows Server 2008. Does this mitigate this vulnerability?
By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration, which mitigates this vulnerability. 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.

How does configuring the Internet zone security setting to High protect me from this vulnerability?
Setting the Internet zone security setting to High protects against this vulnerability by disabling Active Scripting, which is required in order to exploit this vulnerability.

Why is this vulnerability not exploitable on Windows Vista, Windows Server 2008, Windows 7, or Windows Server 2008 R2?
Windows Vista, Windows Server 2008, Windows7, and Windows Server 2008 R2 include architectural improvements in the way that Internet Explorer interacts with the Windows operating system and VBScript. This prevents exploitation of this vulnerability, even though the vulnerable code is present on those systems where users have installed the Windows Help System.

What does the update do?
This security update addresses the vulnerability by modifying the way that the VBScript engine processes help files in protected mode on affected versions of the Windows operating systems. On Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2, there is no known attack vector to exploit this vulnerability, but the update can be installed as a defense-in-depth measure.

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-2010-0483. This vulnerability was described in Microsoft Security Advisory 981169.

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 when this security bulletin was originally issued.

Other Information
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
•

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.
•

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
•

V1.0 (April 13, 2010): Bulletin published.