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From:MICROSOFT <secure_(at)_microsoft.com>
Date:11.08.2010
Subject:Microsoft Security Bulletin MS10-057 - Important Vulnerability in Microsoft Office Excel Could Allow Remote Code Execution (2269707)

Microsoft Security Bulletin MS10-057 - Important
Vulnerability in Microsoft Office Excel Could Allow Remote Code Execution (2269707)
Published: August 10, 2010

Version: 1.0
General Information
Executive Summary

This security update resolves a privately reported vulnerability in Microsoft Office. The vulnerability could allow remote code execution if a user opens a specially crafted Excel file. 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.

This security update is rated Important for all supported editions of Microsoft Office Excel 2002, Microsoft Office Excel 2003, Microsoft Office 2004 for Mac, and Microsoft Office 2008 for Mac; and Open XML File Format Converter for Mac. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The update addresses the vulnerability by changing the way that Microsoft Office Excel parses specially crafted Excel files. 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
Office Suite and Other Software Component Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by this Update
Microsoft Office Suites and Components

Microsoft Office XP Service Pack 3


Microsoft Office Excel 2002 Service Pack 3
(KB2264397)


Remote Code Execution


Important


MS10-038

Microsoft Office 2003 Service Pack 3


Microsoft Office Excel 2003 Service Pack 3
(KB2264403)


Remote Code Execution


Important


MS10-036,
MS10-038
Microsoft Office for Mac

Microsoft Office 2004 for Mac
(KB2284171)


Not applicable


Remote Code Execution


Important


MS10-038

Microsoft Office 2008 for Mac
(KB2284162)


Not applicable


Remote Code Execution


Important


MS10-038

Open XML File Format Converter for Mac
(KB2284179)


Not applicable


Remote Code Execution


Important


MS10-038

Non-Affected Software
Office and Other Software

Microsoft Office Excel 2007 Service Pack 2

Microsoft Office Excel 2010 (32-bit editions)

Microsoft Office Excel 2010 (64-bit editions)

Microsoft Office Excel Viewer Service Pack 2

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

Microsoft Works 9
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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 are Office standalone programs affected by the vulnerability?
An Office standalone program is affected with the same severity rating as the corresponding component in an Office Suite. For example, a standalone installation of Microsoft Office Excel is affected with the same severity rating as an installation of Microsoft Office Excel that was delivered with an Office Suite.

The Office component discussed in this article is part of the Office Suite that I have installed on my system; however, I did not choose to install this specific component. Will I be offered this update?
Yes, if the component discussed in this bulletin was delivered with the version of the Office Suite installed on your system, the system will be offered updates for it whether the component is installed or not. The detection logic used to scan for affected systems is designed to check for updates for all components that were delivered with the particular Office Suite and to offer the updates to a system. Users who choose not to apply an update for a component that is not installed, but is delivered with their version of the Office Suite, will not increase the security risk of that system. On the other hand, users who do choose to install the update will not have a negative impact on the security or performance of a system.

Does the offer to update a non-vulnerable version of Microsoft Office constitute an issue in the Microsoft update mechanism?
No, the update mechanism is functioning correctly in that it detects a lower version of the files on the system than in the update package and thus, offers the update.

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 August bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Excel Memory Corruption Vulnerability - CVE-2010-2562 Aggregate Severity Rating
Microsoft Office Suites and Components

Microsoft Office Excel 2002 Service Pack 3


Important
Remote Code Execution


Important

Microsoft Office Excel 2003 Service Pack 3


Important
Remote Code Execution


Important
Microsoft Office for Mac

Microsoft Office 2004 for Mac


Important
Remote Code Execution


Important

Microsoft Office 2008 for Mac


Important
Remote Code Execution


Important

Open XML File Format Converter for Mac


Important
Remote Code Execution


Important
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Excel Memory Corruption Vulnerability - CVE-2010-2562

A remote code execution vulnerability exists in the way that Microsoft Office Excel handles specially crafted Excel files. 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.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2010-2562.

Mitigating Factors for Excel Memory Corruption Vulnerability - CVE-2010-2562

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:


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, and then convince them to open the specially crafted Excel file.


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.


The vulnerability cannot be exploited automatically through e-mail. For an attack to be successful a user must open an attachment that is sent in an e-mail message.
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Workarounds for Excel Memory Corruption Vulnerability - CVE-2010-2562

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:


Use Microsoft Office File Block policy to block the opening of Office 2003 and earlier documents from unknown or untrusted sources and locations

The following registry scripts can be used to set the File Block policy.

Note Modifying the Registry incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from incorrect modification of the Registry can be solved. Modify the Registry at your own risk.


For Office 2003

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Office\11.
0\Excel\Security\FileOpenBlock]
"BinaryFiles"=dword:00000001

Note In order to use 'FileOpenBlock' with Microsoft Office 2003, all of the latest security updates for Microsoft Office 2003 must be applied.


For 2007 Office system

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.
0\Excel\Security\FileOpenBlock]
"BinaryFiles"=dword:00000001

Note In order to use 'FileOpenBlock' with the 2007 Microsoft Office system, all of the latest security updates for the 2007 Microsoft Office system must be applied.

Impact of workaround. Users who have configured the File Block policy and have not configured a special "exempt directory" as discussed in Microsoft Knowledge Base Article 922848 will be unable to open Office 2003 files or earlier versions in Office 2003 or 2007 Microsoft Office System.

How to undo the workaround.


For Office 2003

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Office\11.
0\Excel\Security\FileOpenBlock]
"BinaryFiles"=dword:00000000


For 2007 Office system

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.
0\Excel\Security\FileOpenBlock]
"BinaryFiles"=dword:00000000


Use the Microsoft Office Isolated Conversion Environment (MOICE) when opening files from unknown or untrusted sources

The Microsoft Office Isolated Conversion Environment (MOICE) helps protect Office 2003 installations by more securely opening Word, Excel, and PowerPoint binary format files.

To install MOICE, you must have Office 2003 or 2007 Office system installed.

To install MOICE, you must also have the Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats. The compatibility pack is available as a free download from the Microsoft Download Center:

Download the FileFormatConverters.exe package now

MOICE requires all updates that are recommended for all Office programs. Visit Microsoft Update to install all recommended updates:

http://update.microsoft.com/microsoftupdate/v6/default.aspx?ln=en-us

Enable MOICE

Note See Microsoft Knowledge Base Article 935865 to use the automated Microsoft Fix it solution to enable or disable this workaround.

To manually enable MOICE, run the commands as specified in the following table. Running the commands will associate the Office application extensions with MOICE.
Command to enable MOICE to be the registered handler

For Word, run the following command from a command prompt:
ASSOC .doc=oice.word.document

For Excel, run the following commands from a command prompt:
ASSOC .XLS=oice.excel.sheet
ASSOC .XLT=oice.excel.template
ASSOC .XLA=oice.excel.addin

For PowerPoint, run the following commands from a command prompt:
ASSOC .PPT=oice.powerpoint.show
ASSOC .POT=oice.powerpoint.template
ASSOC .PPS=oice.powerpoint.slideshow

Note On Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2, run the above commands from an elevated command prompt.

For more information on MOICE, see Microsoft Knowledge Base Article 935865.

Impact of workaround. Office 2003 and earlier formatted documents that are converted to the 2007 Microsoft Office System Open XML format by MOICE will not retain macro functionality. Additionally, documents with passwords or that are protected with Digital Rights Management cannot be converted.

How to undo the workaround. Run the commands to disable MOICE as specified in the table below.
Command to disable MOICE as the registered handler

For Word, run the following command from a command prompt:
ASSOC .doc=Word.Document.8

For Excel, run the following commands from a command prompt:
ASSOC .xls=Excel.Sheet.8
ASSOC .xlt=Excel.Template
ASSOC .xla=Excel.Addin

For PowerPoint, run the following commands from a command prompt:
ASSOC .ppt=PowerPoint.Show.8
ASSOC .PPS=oice.powerpoint.slideshow
ASSOC .pps=PowerPoint.SlideShow.8

Note On Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2, run the above commands from an elevated command prompt.


Do not open Microsoft Office files that you receive from untrusted sources or that you receive unexpectedly from trusted sources

Do not open Microsoft Office files that you receive from untrusted sources or that you receive unexpectedly from trusted sources. This vulnerability could be exploited when a user opens a specially crafted file.
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FAQ for Excel Memory Corruption Vulnerability - CVE-2010-2562

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could take complete control of an affected system remotely. An attacker could then install programs or view, change, or delete data; or create new accounts with full user rights.

What causes the vulnerability?
The vulnerability exists because of the way that Microsoft Office Excel parses the Excel file format when opening a specially crafted Excel file.

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. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
Exploitation of this vulnerability requires that a user open a specially crafted Excel file with an affected version of Microsoft Office Excel.

In an e-mail attack scenario, an attacker could exploit the vulnerability by sending a specially crafted Excel file to the user and by convincing the user to open the file.

In a Web-based attack scenario, an attacker would have to host a Web site that contains an Excel file that is used to attempt to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site, and then convince them to open the specially crafted Excel file.

What systems are primarily at risk from the vulnerability?
Systems where Microsoft Office Excel is used, including workstations and terminal servers, are primarily at risk. Servers could be at more risk if administrators allow users to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do?
This update addresses the vulnerability by changing the way that Microsoft Office Excel parses specially crafted Excel files.

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.

Other Information
Acknowledgments

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


Damián Frizza of Core Security Technologies for reporting the Excel Memory Corruption Vulnerability (CVE-2010-2562)
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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 (August 10, 2010): Bulletin published.

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