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Microsoft Security Bulletin MS08-056 - Moderate

Vulnerability in Microsoft Office Could Allow Information Disclosure (957699)

Published: October 14, 2008 | Updated: November 12, 2008

Version: 1.1

General Information

Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Office. The vulnerability could allow information disclosure if a user clicks a specially crafted CDO URL. An attacker who successfully exploited this vulnerability could inject a client side script in the user's browser that could spoof content, disclose information, or take any action that the user could take on the affected Web site.

This security update is rated Moderate for supported editions of Microsoft Office XP.

The security update addresses the vulnerability by unregistering the CDO protocol. 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 consider applying the security update.

Known Issues. None

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 SoftwareMaximum Security ImpactAggregate Severity RatingBulletins Replaced by this Update
Microsoft Office XP Service Pack 3
(KB956464)
Information DisclosureModerateNone

Non-Affected Software

Office and Other Software
Microsoft Office 2000 Service Pack 3
Microsoft Office 2003 Service Pack 2
Microsoft Office 2003 Service Pack 3
2007 Microsoft Office System
2007 Microsoft Office System Service Pack 1
Microsoft Office Excel/PowerPoint/Word Viewer 2003
Excel/PowerPoint/Word Viewer 2003 Service Pack 3
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Service Pack 1
Microsoft Works 8.0
Microsoft Works 8.5
Microsoft Works 9.0
Microsoft Works Suite 2005
Microsoft Works Suite 2006
Microsoft Office 2004 for Mac
Microsoft Office 2008 for Mac

I do not have all of the affected software installed, but I do have other Microsoft Office applications installed. Why am I being offered the security update?
The vulnerabilities described in this security update exist within Microsoft Office but could not be exploited using one of the applications listed in the Non-Affected Software table. The Microsoft Office applications listed in the Non-Affected Software table use some of the same files as the applications listed in the Affected Software table to which the security update applies. We recommend installing the update to prevent the security update from being offered again.

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.

Vulnerability Information

Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected SoftwareVulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020Aggregate Severity Rating
Microsoft Office XP Service Pack 3 Moderate
Information Disclosure
Moderate
Information Disclosure

A vulnerability exists in the way that Office processes documents using the CDO Protocol (cdo:) and the Content-Disposition: Attachment header. These documents may be incorrectly rendered in the web browser, leading to cross-site scripting.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2008-4020.

Mitigating Factors for Vulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020

  • 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, Internet Explorer on Windows Server 2003 and Windows Server 2008 run 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. See the FAQ subsection of this vulnerability section for more information about Internet Explorer Enhanced Security Configuration.

Workarounds for Vulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020

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:

  • Disable CDO protocol handler
    Disabling the affected protocol will help protect the affected system from attempts to exploit this vulnerability. To disable the affected service, unregister these three registry keys:

    'HKLM\SOFTWARE\Classes\PROTOCOLS\Handler\cdo'
    'HKLM\SOFTWARE\Classes\CDO'
    'HKCR\PROTOCOLS\Handler\cdo'

    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.

FAQ for Vulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020

What is the scope of the vulnerability? 
This is an information disclosure vulnerability. An attacker who successfully exploited this vulnerability could inject a client side script in the user's browser that could spoof content, disclose information, or take any action that the user could take on the affected Web site.

What causes the vulnerability? 
As described in the Microsoft Knowledge Base article 260519, when the header "content-disposition: attachment" is provided, a protocol should raise a File Download dialog box rather than rendering the content. The CDO Protocol (cdo:) does not properly process this header and always renders the content.

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.

How does cross-site scripting work?
Web pages contain text and HTML markup. Text and HTML markup are generated by the server and are interpreted by the client. If untrusted content is introduced into a dynamic page, neither the server nor the client has sufficient information to recognize that this injection has occurred and to take protective measures.

What might an attacker use the vulnerability to do? 
The attacker could spoof content, disclose information, or take any action that the user could take on the affected Web site.

How could an attacker exploit the vulnerability? 
An attacker could exploit this vulnerability by convincing the user to click on a hyperlink to a site that is trusted by the user, that utilizes the content-disposition: attachment flag, and that allows the attacker to post content such as HTML pages.

What systems are primarily at risk from the vulnerability? 
Systems running Microsoft Office XP Service Pack 3 are primarily at risk

What does the update do? 
The update removes the vulnerability by unregistering the CDO Protocol.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure. Microsoft had not received any information to indicate that this vulnerability had been publicly disclosed when this security bulletin was originally issued. This security bulletin addresses the privately disclosed vulnerability as well as additional issues discovered through internal investigations.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received 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.

Update Information

Manage the software and security updates you need to deploy to the servers, desktop, and mobile systems in your organization. For more information see the TechNet Update Management Center. The Microsoft TechNet Security Web site provides additional information about security in Microsoft products.

Security updates are available from Microsoft Update, Windows Update, and Office Update. Security updates are also available from the Microsoft Download Center. You can find them most easily by doing a keyword search for "security update."

Finally, security updates can be downloaded from the Microsoft Update Catalog. The Microsoft Update Catalog provides a searchable catalog of content made available through Windows Update and Microsoft Update, including security updates, drivers and service packs. By searching using the security bulletin number (such as, “MS07-036”), you can add all of the applicable updates to your basket (including different languages for an update), and download to the folder of your choosing. For more information about the Microsoft Update Catalog, see the Microsoft Update Catalog FAQ.

Detection and Deployment Guidance

Microsoft has provided detection and deployment guidance for this month’s security updates. This guidance will also help IT professionals understand how they can use various tools to help deploy the security update, such as Windows Update, Microsoft Update, Office Update, the Microsoft Baseline Security Analyzer (MBSA), the Office Detection Tool, Microsoft Systems Management Server (SMS), and the Extended Security Update Inventory Tool. For more information, see Microsoft Knowledge Base Article 910723.

Microsoft Baseline Security Analyzer

Microsoft Baseline Security Analyzer (MBSA) allows administrators to scan local and remote systems for missing security updates as well as common security misconfigurations. For more information about MBSA, visit Microsoft Baseline Security Analyzer.

The following table provides the MBSA detection summary for this security update.

Software MBSA 2.1
Office XP Service Pack 3Yes

For more information about MBSA 2.1, see MBSA 2.1 Frequently Asked Questions.

Note For customers using legacy software not supported by MBSA 2.0.1, Microsoft Update, and Windows Server Update Services: please visit Microsoft Baseline Security Analyzer and reference the Legacy Product Support section on how to create comprehensive security update detection with legacy tools.

Windows Server Update Services

By using Windows Server Update Services (WSUS), administrators can deploy the latest critical updates and security updates for Windows 2000 operating systems and later, Office XP and later, Exchange Server 2003, and SQL Server 2000. For more information about how to deploy this security update using Windows Server Update Services, visit the Windows Server Update Services Web site.

Systems Management Server

The following table provides the SMS detection and deployment summary for this security update.

SoftwareSMS 2.0SMS 2003 with SUSFPSMS 2003 with ITMUConfiguration Manager 2007
Office XP Service Pack 3YesYesYesYes

For SMS 2.0 and SMS 2003, the SMS SUS Feature Pack (SUSFP), which includes the Security Update Inventory Tool (SUIT), can be used by SMS to detect security updates. See also Downloads for Systems Management Server 2.0.

For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates (ITMU) can be used by SMS to detect security updates that are offered by Microsoft Update and that are supported by Windows Server Update Services. For more information about the SMS 2003 ITMU, see SMS 2003 Inventory Tool for Microsoft Updates. SMS 2003 can also use the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications. For more information about the Office Inventory Tool and other scanning tools, see SMS 2003 Software Update Scanning Tools. See also Downloads for Systems Management Server 2003.

System Center Configuration Manager 2007 uses WSUS 3.0 for detection of updates. For more information about Configuration Manager 2007 Software Update Management, visit System Center Configuration Manager 2007.

For more information about SMS, visit the SMS Web site.

For more detailed information, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.

Update Compatibility Evaluator and Application Compatibility Toolkit

Updates often write to the same files and registry settings required for your applications to run. This can trigger incompatibilities and increase the time it takes to deploy security updates. You can streamline testing and validating Windows updates against installed applications with the Update Compatibility Evaluator components included with Application Compatibility Toolkit 5.0.

The Application Compatibility Toolkit (ACT) contains the necessary tools and documentation to evaluate and mitigate application compatibility issues before deploying Microsoft Windows Vista, a Windows Update, a Microsoft Security Update, or a new version of Windows Internet Explorer in your environment.

Affected Software

For information about the specific security update for your affected software, click the appropriate link:

Office XP (all editions)

Reference Table

The following table contains the security update information for this software. You can find additional information in the subsection, Deployment Information, in this section.

Inclusion in Future Service Packs There are no more service packs planned for this software. The update for this issue may be included in a future update rollup.
Deployment
Installing without user interventionofficeXP-kb956464-fullfile-enu /q:a
Installing without restartingofficeXP-kb956464-fullfile-enu /r:n
Update log fileNot applicable
Further informationFor detection and deployment, see the earlier section, Detection and Deployment Tools and Guidance.

For features you can selectively install, see the Office Features for Administrative Installations subsection in this section.
Restart Requirement
Restart required?This update does not require a restart.
HotpatchingNot applicable
Removal Information This security update cannot be uninstalled.
File Information See Microsoft Knowledge Base Article 957699
Registry Key Verification Not applicable

Office Features

The following table contains the list of feature names (case sensitive) that must be reinstalled for the update. To install all features, you can use REINSTALL=ALL or you can install the following features:

ProductFeature
ACCESS, FP, OUTLOOK, PPT, ACCESSRT, PUBProductFiles
PIPC1, PROPLUS, PRO, SBE, STD, STDEDUProductFiles

Note Administrators working in managed environments can find complete resources for deploying Office updates in an organization at the Office Admin Update Center. At that site, scroll down and look under the Update Resources section for the software version you are updating. The Windows Installer Documentation also provides more information about the parameters supported by Windows Installer.

Deployment Information

Installing the Update

You can install the update from the appropriate download link in the Affected and Non-Affected Software section. If you installed your application from a server location, the server administrator must instead update the server location with the administrative update and deploy that update to your system. For more information about Administrative Installation Points, refer to the Office Administrative Installation Point information in the Detection and deployment Tools and Guidance subsection.

This security update requires that Windows Installer 2.0 or later be installed on the system. All supported versions of Windows include Windows Installer 2.0 or a later version.

To install the latest version of Windows Installer, visit one of the following Microsoft Web sites:

For more information about the terminology that appears in this bulletin, such as hotfix, see Microsoft Knowledge Base Article 824684.

This security update supports the following setup switches.

Supported Security Update Installation Switches
SwitchDescription
/q Specifies quiet mode, or suppresses prompts, when files are being extracted.
/q:u Specifies user-quiet mode, which presents some dialog boxes to the user.
/q:a Specifies administrator-quiet mode, which does not present any dialog boxes to the user.
/t:path Specifies the target folder for extracting files.
/c Extracts the files without installing them. If /t:path is not specified, you are prompted for a target folder.
/c:path Overrides the install command that is defined by author. Specifies the path and name of the Setup.inf or .exe file.
/r:n Never restarts the system after installation.
/r:I Prompts the user to restart the system if a restart is required, except when used with /q:a.
/r:a Always restarts the system after installation.
/r:s Restarts the system after installation without prompting the user.
/n:v No version checking - Install the program over any earlier version.

Note You can combine these switches into one command. For backward compatibility, the security update also supports the setup switches that the earlier version of the Setup program uses. For more information about the supported installation switches, see Microsoft Knowledge Base Article 262841.

Removing the Update

This security update cannot be uninstalled.

Verifying That the Update Has Been Applied

  • Microsoft Baseline Security Analyzer

    To verify that a security update has been applied to an affected system, you may be able to use the Microsoft Baseline Security Analyzer (MBSA) tool. See the “Microsoft Baseline Security Analyzer” heading under the section, Detection and Deployment Tools and Guidance, earlier in this bulletin for more information.

  • File Version Verification

    Because there are several versions and editions of Microsoft Windows, the following steps may be different on your system. If they are, see your product documentation to complete these steps.

    1. Click Start, and then click Search.
    2. In the Search Results pane, click All files and folders under Search Companion.
    3. In the All or part of the file name box, type a file name from the appropriate file information table, and then click Search.
    4. In the list of files, right-click a file name from the appropriate file information table, and then click Properties.

      Note Depending on the version of the operating system or programs installed, some of the files that are listed in the file information table may not be installed.
    5. On the Version tab, determine the version of the file that is installed on your system by comparing it to the version that is documented in the appropriate file information table.

      Note Attributes other than the file version may change during installation. Comparing other file attributes to the information in the file information table is not a supported method of verifying that the update has been applied. Also, in certain cases, files may be renamed during installation. If the file or version information is not present, use one of the other available methods to verify update installation.

Other Information

Acknowledgments

Microsoft thanks the following for working with us to help protect customers:

  • NetAgent Co., Ltd. for reporting the Vulnerability in Content Disposition Header Vulnerability (CVE-2008-4020).

Support

  • Customers in the U.S. and Canada can receive technical support from Microsoft Product Support Services at 1-866-PCSAFETY. There is no charge for support calls that are associated with security updates.
  • 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 14, 2008): Bulletin published.
  • V1.1 (November 12, 2008): Corrected the removal information in the section, Security Update Deployment, to state that this security update cannot be uninstalled.

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