Microsoft Security Bulletin MS08-056 - Moderate
Vulnerability in Microsoft Office Could Allow Information Disclosure (957699)
Published: October 14, 2008 | Updated: November 12, 2008
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.
|Office Suite and Other Software||Maximum Security Impact||Aggregate Severity Rating||Bulletins Replaced by this Update|
|Microsoft Office XP Service Pack 3
|Affected Software||Vulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020||Aggregate Severity Rating|
|Microsoft Office XP Service Pack 3||Moderate
Vulnerability in Content-Disposition Header Vulnerability - CVE-2008-4020
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?
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.
Detection and Deployment Tools and Guidance
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.
|Office XP Service Pack 3||Yes|
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.
|Software||SMS 2.0||SMS 2003 with SUSFP||SMS 2003 with ITMU||Configuration Manager 2007|
|Office XP Service Pack 3||Yes||Yes||Yes||Yes|
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.
Security Update Deployment
For information about the specific security update for your affected software, click the appropriate link:
Office XP (all editions)
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.|
|Installing without user intervention||officeXP-kb956464-fullfile-enu /q:a|
|Installing without restarting||officeXP-kb956464-fullfile-enu /r:n|
|Update log file||Not applicable|
|Further information||For 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 required?||This update does not require a restart.|
|Removal Information||This security update cannot be uninstalled.|
|File Information||See Microsoft Knowledge Base Article 957699|
|Registry Key Verification||Not applicable|