Microsoft Security Bulletin MS06-059 Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (924164)

Microsoft Security Bulletin MS06-059
Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (924164)
Published: October 10, 2006

Version: 1.0
Summary

Who Should Read this Document: Customers who use Microsoft Excel

Impact of Vulnerability: Remote Code Execution

Maximum Severity Rating: Critical

Recommendation: Customers should apply the update immediately

Security Update Replacement: This bulletin replaces a prior security update. See the frequently asked questions (FAQ) section of this bulletin for the complete list.

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:
•

Microsoft Office 2000 Service Pack 3
•

Microsoft Excel 2000 — Download the update (KB923090)
•

Microsoft Office XP Service Pack 3
•

Microsoft Excel 2002 — Download the update (KB923089)
•

Microsoft Office 2003 Service Pack 1 or Service Pack 2
•

Microsoft Office Excel 2003 — Download the update (KB923088)
•

Microsoft Office Excel Viewer 2003 - Download the update (KB923088)
•

Microsoft Office 2004 for Mac
•

Microsoft Excel 2004 for Mac - Download the update (KB924999)
•

Microsoft Office v. X for Mac
•

Microsoft Excel v. X for Mac - Download the update (KB924998)
•

Microsoft Works Suites:
•

Microsoft Works Suite 2004 - Download the update (KB923089) (same as the Microsoft Excel 2002 update)
•

Microsoft Works Suite 2005 - Download the update (KB923089) (same as the Microsoft Excel 2002 update)
•

Microsoft Works Suite 2006 - Download the update (KB923089) (same as the Microsoft Excel 2002 update)

The software in this list has been tested to determine whether the versions are affected. Other versions either no longer include security update support or may not be affected. To determine the support life cycle for your product and version, visit the Microsoft Support Lifecycle Web site.
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General Information

Executive Summary

Executive Summary:

This update addresses several newly discovered, privately reported and public vulnerabilities. Each vulnerability is documented in this bulletin in its own "Vulnerability Details" section.

When using vulnerable versions of Office, if a user were logged on with administrative user rights, an attacker who successfully exploited these vulnerabilities could take complete control of the client workstation. 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.

We recommend that customers apply the update immediately.

Severity Ratings and Vulnerability Identifiers:
Vulnerability Identifiers Impact of Vulnerability Microsoft Excel 2000 Microsoft Excel 2002 Microsoft Excel 2003 and Excel Viewer 2003 Microsoft Excel 2004 for Mac and Excel v.X for Mac

Excel Malformed DATETIME Record Vulnerability - CVE-2006-2387

Remote Code Execution

Critical

Important

Important

Important

Excel Malformed STYLE Record Vulnerability - CVE-2006-3431

Remote Code Execution

Critical

Important

Important

Important

Excel Handling of Lotus 1-2-3 File Vulnerability - CVE-2006-3867

Remote Code Execution

Critical

Important

Important

Important

Excel Malformed COLINFO Record Vulnerability - CVE-2006-3875

Remote Code Execution

Critical

Important

Important

Important

Aggregate Severity of All Vulnerabilities

Critical

Important

Important

Important

This assessment is based on the types of systems that are affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them.

Note The severity ratings for Microsoft Works Suite maps to the Microsoft Excel versions as follows:
•

The Microsoft Works Suite 2004 severity rating is the same as the Microsoft Excel 2002 severity rating.
•

The Microsoft Works Suite 2005 severity rating is the same as the Microsoft Excel 2002 severity rating.
•

The Microsoft Works Suite 2006 severity rating is the same as the Microsoft Excel 2002 severity rating.
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Frequently Asked Questions (FAQ) Related to This Security Update

Why does this update address several reported security vulnerabilities?
This update addresses 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 can install only this update.

What updates does this release replace?
This security update replaces a prior security update. The security bulletin ID and affected operating systems are listed in the following table.
Bulletin ID Microsoft Excel 2000 Microsoft Excel 2002 Microsoft Excel 2003 and Excel Viewer 2003 Microsoft Excel 2004 for Mac and Excel v.X for Mac

MS06-037

Replaced

Replaced

Replaced

Replaced

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine whether this update is required?
The following table provides the MBSA detection summary for this security update.
Software MBSA 1.2.1 MBSA 2.0

Microsoft Excel 2000

Yes

No

Microsoft Excel 2002

Yes

Yes

Microsoft Excel 2003

Yes

Yes

Microsoft Excel 2004 for Mac

No

No

Microsoft Excel v. X for Mac

No

No

Note MBSA 1.2.1 uses an integrated version of the Office Detection Tool (ODT) which does not support remote scans of this security update. For more information about MBSA, visit the MBSA Web site.

For more information about the programs that Microsoft Update and MBSA 2.0 currently do not detect, see Microsoft Knowledge Base Article 895660.

For more detailed information about detection and deployment guidance, see Microsoft Knowledge Base Article 910723.

Can I use Systems Management Server (SMS) to determine whether this update is required?
The following table provides the SMS detection summary for this security update.
Software SMS 2.0 SMS 2003

Microsoft Excel 2000

Yes

Yes

Microsoft Excel 2002

Yes

Yes

Microsoft Excel 2003

Yes

Yes

Microsoft Excel 2004 for Mac

No

No

Microsoft Excel v. X for Mac

No

No

SMS uses MBSA for detection. Therefore, SMS has the same limitation that is listed earlier in this bulletin related to programs that MBSA does not detect.

For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool, can be used by SMS to detect security updates. SMS SUIT uses the MBSA 1.2.1 engine for detection. For more information about the Security Update Inventory Tool, visit the following Microsoft Web site. For more information about the limitations of the Security Update Inventory Tool, see Microsoft Knowledge Base Article 306460. The SMS SUS Feature Pack also includes the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates 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 Inventory Tool for Microsoft Updates, visit the following Microsoft Web site. SMS 2003 can also use the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

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

Excel Malformed DATETIME Record Vulnerability - CVE-2006-2387:

A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed DATETIME record.

If a user were 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 affected than users who operate with administrative user rights.

Mitigating Factors for Excel Malformed DATETIME Record Vulnerability - CVE-2006-2387:
•

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 impacted than users who operate with administrative user rights.
•

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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.
•

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.
•

Users who have installed and are using the Office Document Open Confirmation Tool for Office 2000 will be prompted with Open, Save, or Cancel before opening a document. The features of the Office Document Open Confirmation Tool are incorporated in Office XP and Office 2003.
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Workarounds Excel Malformed DATETIME Record Vulnerability - CVE-2006-2387:
•

Do not open or save Microsoft Excel 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 Malformed DATETIME Record Vulnerability - CVE-2006-2387:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed DATETIME record.

If a user were 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 affected than users who operate with administrative user rights.

What causes the vulnerability?
Excel does not perform sufficient data validation when processing the contents of an .xls file. When Excel opens a specially crafted Excel file and parses a malformed DATETIME record, it may corrupt system memory in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take any action on the system that the user who opened the file could take.

How could an attacker exploit the vulnerability?
In an e-mail attack scenario, an attacker could exploit the vulnerability by sending a specially-crafted file to the user and by persuading 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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if users who have sufficient administrative permissions are given the ability to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do?
The update removes the vulnerability by modifying the way that Excel parses the file and validates a record before passing it to the allocated buffer.

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 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.
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Excel Malformed STYLE Record Vulnerability - CVE-2006-3431:

A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed STYLE record.

If a user were 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 affected than users who operate with administrative user rights.

Mitigating Factors for Excel Malformed STYLE Record Vulnerability - CVE-2006-3431:
•

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 impacted than users who operate with administrative user rights.
•

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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.
•

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.
•

Users who have installed and are using the Office Document Open Confirmation Tool for Office 2000 will be prompted with Open, Save, or Cancel before opening a document. The features of the Office Document Open Confirmation Tool are incorporated in Office XP and Office 2003.
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Workarounds for Excel Malformed STYLE Record Vulnerability - CVE-2006-3431:

Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
•

Do not open or save Microsoft Excel 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.
•

Download and run the "Office 2003 Add-in: Desktop Language Settings" tool to change the configured language settings for Office.
•

Modify the value of “InstallLanguage” to Non-Double Byte characters (DBCS)
Modifying the “InstallLanguage” registry key helps protect the affected system from attempts to exploit this vulnerability.

Note Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use 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.

For Windows 2000

Note Make a note of the permissions that are listed in the dialog box so that you can restore them to their original values at a later time

Click Start, click Run, type "regedt32" (without the quotation marks), and then click OK.

Expand HKEY_CURRENT_USER, expand the following subkeys; Software, Microsoft, Office, 11.0, Common.

Click LanguageResources, and then double-click InstallLanguagevalue to bring up the “Edit DWORD value” dialog box.

Change the value to one that represents a non East Asian language value such as U.S. English's value of 409 and click OK.

Note For a list of other Language ID's refer to the following Knowledge Base Article 324097.

For Windows XP Service Pack 1 or later operating systems

Note Make a note of the permissions that are listed in the dialog box so that you can restore them to their original values at a later time

Click Start, click Run, type "regedit" (without the quotation marks), and then click OK.

Expand HKEY_CURRENT_USER, expand the following subkeys; Software, Microsoft, Office, 11.0, Common.

Click LanguageResources, and then double-click InstallLanguagevalue to bring up the “Edit DWORD value” dialog box.

Change the value to one that represents a non East Asian language value such as U.S. English's value of 409 and click OK.

Note For a list of other Language ID's refer to the following Knowledge Base Article 324097.

Impact of Workaround: Special Unicode characters in spreadsheets may fail to display as the proper symbol.
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FAQ for Excel Malformed STYLE Record Vulnerability - CVE-2006-3431:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed STYLE record.

If a user were 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 affected than users who operate with administrative user rights.

What causes the vulnerability?
Excel does not perform sufficient data validation when processing the contents of an .xls file. When Excel opens a specially crafted Excel file and parses a malformed STYLE record, it may corrupt system memory in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take any action on the system that the user who opened the file could take.

How could an attacker exploit the vulnerability?
In an e-mail attack scenario, an attacker could exploit the vulnerability by sending a specially crafted file to the user and by persuading 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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if users who have sufficient administrative permissions are given the ability to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do?
The update removes the vulnerability by modifying the way that Excel validates the length of a record before it passes the message to the allocated buffer.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
Yes. While the initial report was provided through responsible disclosure, the vulnerability was later disclosed publicly. This security bulletin addresses the publicly 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 seen examples of proof of concept code published publicly but 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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Excel Handling of Lotus 1-2-3 File Vulnerability - CVE-2006-3867:

A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel handles a Lotus 1-2-3 file.

If a user were 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 affected than users who operate with administrative user rights.

Mitigating Factors for Excel Handling of Lotus 1-2-3 File Vulnerability - CVE-2006-3867:
•

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 impacted than users who operate with administrative user rights.
•

In a Web-based attack scenario, an attacker would have to host a Web site that contains a Lotus 1-2-3 file which Excel opens 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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.
•

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.
•

Users who have installed and are using the Office Document Open Confirmation Tool for Office 2000 will be prompted with Open, Save, or Cancel before opening a document. The features of the Office Document Open Confirmation Tool are incorporated in Office XP and Office 2003.
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Workarounds for Excel Handling of Lotus 1-2-3 File Vulnerability - CVE-2006-3867:
•

Do not open or save Lotus 1-2-3 files using Microsoft Excel 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 Handling of Lotus 1-2-3 File Vulnerability - CVE-2006-3867:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel handles a Lotus 1-2-3 file.

If a user were 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 affected than users who operate with administrative user rights.

What causes the vulnerability?
When Excel opens a specially crafted Lotus 1-2-3 file, it may corrupt system memory in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take any action on the system that the user who opened the file could take.

How could an attacker exploit the vulnerability?
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 impacted than users who operate with administrative user rights.

In a Web-based attack scenario, an attacker would have to host a Web site that contains a Lotus 1-2-3 file which Excel opens 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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if users who have sufficient administrative permissions are given the ability to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do?
The update removes the vulnerability by modifying the way that Excel validates the length of a record before it passes the message to the allocated buffer.

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-2006-3867.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had seen examples of proof of concept code published publicly but 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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Malformed COLINFO Record Vulnerability - CVE-2006-3875:

A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed COLINFO record.

If a user were 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 affected than users who operate with administrative user rights.

Mitigating Factors for Malformed COLINFO Record Vulnerability - CVE-2006-3875:
•

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 impacted than users who operate with administrative user rights.
•

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 malicious Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.
•

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.
•

Users who have installed and are using the Office Document Open Confirmation Tool for Office 2000 will be prompted with Open, Save, or Cancel before opening a document. The features of the Office Document Open Confirmation Tool are incorporated in Office XP and Office 2003.
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Workarounds for Malformed COLINFO Record Vulnerability - CVE-2006-3875:
•

Do not open or save Microsoft Excel 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 Malformed COLINFO Record Vulnerability - CVE-2006-3875:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed COLINFO record.

If a user were 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 affected than users who operate with administrative user rights.

What causes the vulnerability?
Excel does not perform sufficient data validation when processing the contents of an .xls file. When Excel opens a specially crafted Excel file and parses a malformed COLINFO record, it may corrupt system memory in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take any action on the system that the user who opened the file could take.

How could an attacker exploit the vulnerability?
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 persuade 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.

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

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers are primarily at risk. Servers could be at more risk if users who have sufficient administrative permissions are given the ability to log on to servers and to run programs. However, best practices strongly discourage allowing this.

What does the update do?
The update removes the vulnerability by modifying the way that Excel validates the length of a record before it passes the message to the allocated buffer.

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 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.

Acknowledgments

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

Manuel Santamarina Suarez working with Zero Day Initiative (ZDI) and TippingPoint for reporting the Excel File Format Parsing Overflow Vulnerability - CVE-2006-2387.
•

NSFocus Security Team for reporting the Excel Malformed COLINFO Record Vulnerability - CVE-2006-3875.

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 10, 2006): Bulletin published.