Microsoft Security Bulletin MS10-072 - Important Vulnerabilities in SafeHTML Could Allow Information Disclosure (2412048)

Microsoft Security Bulletin MS10-072 - Important
Vulnerabilities in SafeHTML Could Allow Information Disclosure (2412048)
Published: October 12, 2010

Version: 1.0
General Information
Executive Summary

This security update resolves one publicly disclosed vulnerability and one privately reported vulnerability in Microsoft SharePoint and Windows SharePoint Services. The vulnerabilities could allow information disclosure if an attacker submits specially crafted script to a target site using SafeHTML.

This security update is rated Important for Microsoft SharePoint Services 3.0, Microsoft SharePoint Foundation 2010, and Microsoft Office Web Apps; and all supported editions of Microsoft Office SharePoint Server 2007, and Microsoft Groove Server 2010. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The update addresses the vulnerabilities by modifying the way that SafeHTML sanitizes HTML content. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section, Vulnerability Information.

Recommendation. Microsoft recommends that customers apply the update at the earliest opportunity.

Known Issues. None
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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
Software Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update
Windows SharePoint Services and Microsoft SharePoint Foundation

Microsoft Windows SharePoint Services 3.0 Service Pack 2 (32-bit versions)
(KB2345304)

Information Disclosure

Important

MS10-039

Microsoft Windows SharePoint Services 3.0 Service Pack 2 (64-bit versions)
(KB2345304)

Information Disclosure

Important

MS10-039

Microsoft SharePoint Foundation 2010
(KB2345322)

Information Disclosure

Important

None
Microsoft SharePoint Server and Microsoft Groove Server

Microsoft Office SharePoint Server 2007 Service Pack 2 (32-bit editions)[1]
(KB2345212)

Information Disclosure

Important

MS10-039

Microsoft Office SharePoint Server 2007 Service Pack 2 (64-bit editions)[1]
(KB2345212)

Information Disclosure

Important

MS10-039

Microsoft Groove Server 2010
(KB2346298)

Information Disclosure

Important

None
Microsoft Office Web Apps

Microsoft Office Web Apps
(KB2346411)

Information Disclosure

Important

None

[1]For supported editions of Microsoft Office SharePoint Server 2007, in addition to security update package KB2345212, customers also need to install the security update for Microsoft Windows SharePoint Services 3.0 (KB2345304) to be protected from the vulnerabilities described in this bulletin.

Non-Affected Software
Office and Other Software

Microsoft Windows SharePoint Services 2.0

Microsoft SharePoint Portal Server 2001 Service Pack 3

Microsoft SharePoint Portal Server 2003 Service Pack 3

Microsoft SharePoint Server 2010

Microsoft Groove 2007

Microsoft SharePoint Workspace
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Frequently Asked Questions (FAQ) Related to This Security Update

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.

How is this security update related to MS10-071?
The HTML Sanitization Vulnerability (CVE-2010-3243) and HTML Sanitization Vulnerability (CVE-2010-3324) are addressed by this update (MS10-072) and the Cumulative Security Update for Internet Explorer (MS10-071) update.

Two different updates are needed because the modifications that are required to address the issue are located in different Microsoft products. This update (MS10-072) addresses the vulnerabilities in affected Microsoft productivity software and MS10-071 addresses the vulnerabilities in Internet Explorer.

MS10-079 also describes vulnerabilities in Microsoft Office Web Apps. How does MS10-079 relate to this bulletin (MS10-072)?
The security update package in this bulletin, MS10-072, for Microsoft Office Web Apps (KB2346411) also addresses a vulnerability described in MS10-079. Users with Microsoft Office Web Apps installed will only need to install the KB2346411 security update package once.

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.

What is Microsoft Groove Server 2010?
Microsoft Groove Server 2010 is a Windows-based software package that provides comprehensive services for managing Microsoft SharePoint Workspace. Groove Server 2010 contains two components: Groove Server 2010 Manager and Groove Server 2010 Relay, each of which runs on a Windows server on an enterprise network.

What is Microsoft Office Web Apps?
Microsoft Office Web Apps is the online companion to Office Word, Excel, PowerPoint, and OneNote applications that enables users regardless of their location to access documents and edit documents. Users can view, share, and work on documents with others online across personal computers, mobile phones, and the Web. Office Web Apps is available to business customers with Microsoft Office 2010 volume licensing and document management solutions based on Microsoft SharePoint 2010 products.

Where are updates for Microsoft Office Web Apps applied?
Customers who have deployed Microsoft Office Web Apps in a SharePoint environment will need to apply the updates for Microsoft Office Web Apps on the servers on which those components are installed. For more information about deploying Microsoft Web Apps, see the Microsoft TechNet article, Understanding Office Web Apps.

Note The update for Microsoft Office Web Apps does not apply to the client workstations that use a Web browser to access Microsoft Office Web Apps.

What is Microsoft SharePoint Foundation 2010?
SharePoint Foundation 2010 is the new version of Microsoft Windows SharePoint Services. It is the essential solution for organizations that need a secure, manageable, web-based collaboration platform. SharePoint helps teams stay connected and productive by providing easy access to the people, documents, and information that they need to make well-informed decisions and get work done. Use SharePoint Foundation to coordinate schedules, organize documents, and participate in discussions through team workspaces, blogs, wikis, and document libraries on the platform that is the underlying infrastructure for SharePoint Server.

What is Microsoft Windows SharePoint Services 3.0?
Windows SharePoint Services 3.0 provides a platform for collaborative applications, offering a common framework for document management and a common repository for storing documents of all types. It exposes key Windows Server services like Windows Workflow Services and Windows Rights Management Services.

Windows SharePoint Services 3.0 is provided as a free download for supported editions of Windows Server 2003 and Windows Server 2008.

How is Microsoft Windows SharePoint Services 3.0 related to Microsoft Office SharePoint Server 2007?
Microsoft Office SharePoint Server 2007 is an integrated suite of server capabilities built on top of Windows SharePoint Services 3.0.

In what configurations will I need to apply the different updates?
You will need to apply one or both updates, depending on which SharePoint product is installed on your system. For systems with only Microsoft Windows SharePoint Services 3.0 installed, you will need to apply the KB2345304 update. For systems with Microsoft Office SharePoint Server 2007 installed, you will need to apply both the KB2345212 and KB2345304 updates. There is no configuration where you can only have Microsoft Office SharePoint Server 2007 and not Microsoft Windows SharePoint Services 3.0.

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 October bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software HTML Sanitization Vulnerability - CVE-2010-3243 HTML Sanitization Vulnerability - CVE-2010-3324 Aggregate Severity Rating
Windows SharePoint Services and Microsoft SharePoint Foundation

Microsoft Windows SharePoint Services 3.0 Service Pack 2 (32-bit versions)

Important
Information Disclosure

Important
Information Disclosure

Important

Microsoft Windows SharePoint Services 3.0 Service Pack 2 (64-bit versions)

Important
Information Disclosure

Important
Information Disclosure

Important

Microsoft SharePoint Foundation 2010

Not applicable

Important
Information Disclosure

Important
Microsoft SharePoint Server and Microsoft Groove Server

Microsoft Office SharePoint Server 2007 Service Pack 2 (32-bit editions)

Important
Information Disclosure

Important
Information Disclosure

Important

Microsoft Office SharePoint Server 2007 Service Pack 2 (64-bit editions)

Important
Information Disclosure

Important
Information Disclosure

Important

Microsoft Groove Server 2010

Not applicable

Important
Information Disclosure

Important
Microsoft Office Web Apps

Microsoft Office Web Apps

Not applicable

Important
Information Disclosure

Important
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HTML Sanitization Vulnerability - CVE-2010-3243

An information disclosure vulnerability exists in the way that HTML is filtered that could allow an attacker to perform cross-site scripting attacks and run script in the security context of the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-3243.

Mitigating Factors for HTML Sanitization Vulnerability - CVE-2010-3243

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:
•

Only sites that use SafeHTML to sanitize HTML are affected.
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Workarounds for HTML Sanitization Vulnerability - CVE-2010-3243

Microsoft has not identified any workarounds for this vulnerability.
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FAQ for HTML Sanitization Vulnerability - CVE-2010-3243

What is the scope of the vulnerability?
This is an information disclosure vulnerability. An attacker who successfully exploited the vulnerability could perform persistent cross-site scripting attacks against users of a site that is filtering HTML content via SafeHTML.

What causes the vulnerability?
The vulnerability is caused by the way that the SafeHTML function sanitizes HTML.

What is cross-site scripting?
Cross-site scripting (XSS) is a class of security vulnerability that can enable an attacker to inject script code into a user's session with a Web site. The vulnerability can affect Web servers that dynamically generate HTML pages. If these servers embed browser input in the dynamic pages that they send back to the browser, these servers can be manipulated to include maliciously supplied content in the dynamic pages. This can allow malicious script to be executed. Web browsers may perpetuate this problem through their assumptions of "trusted" sites and their use of cookies to maintain persistent state with the Web sites that they frequent. An XSS attack does not modify Web site content. Instead, it inserts new, malicious script that can execute at the browser in the context that is associated with a trusted server.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited the vulnerability could perform cross-site scripting attacks against users of a targeted site that uses SafeHTML to sanitize HTML. An attacker could then potentially run scripts on behalf of the targeted site's users.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker must have the ability to submit a specially crafted script to a target site using SafeHTML. Due to the vulnerability, in specific situations the specially crafted script is not properly sanitized, which subsequently could lead to an attacker-supplied script being run in the security context of a user who views the malicious content.

For cross-site scripting attacks, this vulnerability requires that a user be visiting a compromised site for any malicious action to occur. For instance, after an attacker has successfully submitted specially crafted script to the targeted site using SafeHTML, any Web page on that site that contains the specially crafted script is a potential vector for persistent cross-site scripting attacks. When a user visits a Web page that contains the specially crafted script, the script could be run in the security context of the user.

What systems are primarily at risk from the vulnerability?
Systems where users connect to a server that uses SafeHTML to sanitize HTML content, such as workstations or terminal servers, are primarily at risk.

What does the update do?
The update addresses the vulnerability by modifying the way that SafeHTML sanitizes HTML content.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through coordinated vulnerability 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 when this security bulletin was originally issued.
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HTML Sanitization Vulnerability - CVE-2010-3324

An information disclosure vulnerability exists in the way that the SafeHTML function sanitizes HTML. An attacker who successfully exploited this vulnerability could perform cross-site scripting attacks and run script in the security context of the logged-on user.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-3324.

Mitigating Factors for HTML Sanitization Vulnerability - CVE-2010-3324

Microsoft has not identified any mitigating factors for this vulnerability.
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Workarounds for HTML Sanitization Vulnerability - CVE-2010-3324

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:
•

Read e-mails in plain text

To help protect yourself from the e-mail attack vector, read e-mail messages in plain text format.

Microsoft Office Outlook 2002 users who have applied Office XP Service Pack 1 or a later version and Microsoft Office Outlook Express 6 users who have applied Internet Explorer 6 Service Pack 1 or a later version can enable this setting and view e-mail messages that are not digitally signed or e-mail messages that are not encrypted in plain text only.

Digitally signed e-mail messages or encrypted e-mail messages are not affected by the setting and may be read in their original formats. For more information about how to enable this setting in Outlook 2002, see Microsoft Knowledge Base Article 307594.

For information about this setting in Outlook Express 6, see Microsoft Knowledge Base Article 291387.

Impact of workaround. E-mail messages that are viewed in plain text format will not contain pictures, specialized fonts, animations, or other rich content. Additionally:
•

The changes are applied to the preview pane and to open messages.
•

Pictures become attachments so that they are not lost.
•

Because the message is still in Rich Text or HTML format in the store, the object model (custom code solutions) may behave unexpectedly.
•

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 Internet Options on the Tools menu.

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 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 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 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 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.

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 HTML Sanitization Vulnerability - CVE-2010-3324

What is the scope of the vulnerability?
This is an information disclosure vulnerability. An attacker who successfully exploited the vulnerability could perform persistent cross-site scripting attacks against users of a site that is filtering HTML content via SafeHTML.

What causes the vulnerability?
The vulnerability is caused by the way that the SafeHTML function sanitizes HTML.

What is cross-site scripting?
Cross-site scripting (XSS) is a class of security vulnerability that can enable an attacker to inject script code into a user's session with a Web site. The vulnerability can affect Web servers that dynamically generate HTML pages. If these servers embed browser input in the dynamic pages that they send back to the browser, these servers can be manipulated to include maliciously supplied content in the dynamic pages. This can allow malicious script to be executed. Web browsers may perpetuate this problem through their assumptions of "trusted" sites and their use of cookies to maintain persistent state with the Web sites that they frequent. An XSS attack does not modify Web site content. Instead, it inserts new, malicious script that can execute at the browser in the context that is associated with a trusted server.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited the vulnerability could perform cross-site scripting attacks against users of a targeted site that uses SafeHTML to sanitize HTML. An attacker could then potentially run script on behalf of a victim user on the site.

How could an attacker exploit the vulnerability?
To exploit this vulnerability, an attacker must have the ability to submit a specially crafted script to a target site using SafeHTML. Due to the vulnerability, in specific situations the specially crafted script is not properly sanitized, which subsequently could lead to an attacker-supplied script being run in the security context of a user who views the malicious content.

For cross-site scripting attacks, this vulnerability requires that a user be visiting a compromised site for any malicious action to occur. For instance, after an attacker has successfully submitted specially crafted script to the targeted site using SafeHTML, any Web page on that site that contains the specially crafted script is a potential vector for persistent cross-site scripting attacks. When a user visits a Web page that contains the specially crafted script, the script could be run in the security context of the user.

What systems are primarily at risk from the vulnerability?
Systems where users connect to a server that uses SafeHTML to sanitize HTML content, such as workstations or terminal servers, are primarily at risk.

What does the update do?
The update addresses the vulnerability by modifying the way that SafeHTML sanitizes HTML content.

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-2010-3324.

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:
•

Sirdarckcat of Google Inc. for reporting the HTML Sanitization Vulnerability (CVE-2010-3243)
•

Mario Heiderich for reporting the HTML Sanitization Vulnerability (CVE-2010-3324)
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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 (October 12, 2010): Bulletin published.