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From:MICROSOFT <secure_(at)_microsoft.com>
Date:09.01.2007
Subject:Microsoft Security Bulletin MS07-002 Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (927198)

Microsoft Security Bulletin MS07-002
Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (927198)
Published: January 9, 2007

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 (KB925524)


Microsoft Office XP Service Pack 3


Microsoft Excel 2002 Download the update (KB925523)


Microsoft Office 2003 Service Pack 2


Microsoft Excel 2003 Download the update (KB925257)


Microsoft Office Excel Viewer 2003 Download the update (KB925525)


Microsoft Works Suites:


Microsoft Works Suite 2004 - Download the update (KB925523) (same as the Microsoft Excel 2002 update)


Microsoft Works Suite 2005 - Download the update (KB925523) (same as the Microsoft Excel 2002 update)


Microsoft Office 2004 for Mac - Download the update (KB930402)


Microsoft Office v. X for Mac - Download the update (KB930403)

Non-Affected Software:


2007 Microsoft Office system


Microsoft Office Excel 2007


Microsoft Works Suites:


Microsoft Works Suite 2006

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 resolves several newly discovered, privately reported vulnerabilities. Each vulnerability is documented in its own subsection in the "Vulnerability Details" section of this bulletin.

An attacker who successfully exploited the most severe of these vulnerabilities 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.

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 Office Excel 2003 Microsoft Excel Viewer 2003 Microsoft Excel 2004 for Mac and Excel v.X for Mac

Excel Malformed IMDATA Record Vulnerability - CVE-2007-0027


Remote Code Execution


Critical


Important


None


None


Important

Excel Malformed Record Vulnerability - CVE-2007-0028


Remote Code Execution


Critical


Important


Important


Important


Important

Excel Malformed String Vulnerability - CVE 2007-0029


Remote Code Execution


Critical


Important


Important


Important


Important

Excel Malformed Column Record Vulnerability - CVE-2007-0030


Remote Code Execution


Critical


Important


Important


Important


Important

Excel Malformed Palette Record Vulnerability - CVE-2007-0031


Remote Code Execution


Critical


Important


Important


None


Important

Aggregate Severity of All Vulnerabilities





Critical


Important


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 and 2005 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 contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files. Instead of having to install several updates that are almost the same, customers 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 applications 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 X for Mac

MS06-059


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.
Product MBSA 1.2.1 MBSA 2.0

Microsoft Excel 2000 Service Pack 3


Yes


No

Microsoft Excel 2002 Service Pack 3


Yes


Yes

Microsoft Excel 2003 Service Pack 2


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.

Note Microsoft Works 2004 and 2005 updates are the same as the Microsoft Excel 2002 update.

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, 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.
Product SMS 2.0 SMS 2003

Microsoft Excel 2000 Service Pack 3


Yes


Yes

Microsoft Excel 2002 Service Pack 3


Yes


Yes

Microsoft Excel 2003 Service Pack 2


Yes


Yes

Microsoft Excel 2004 for Mac


No


No

Microsoft Excel v. X for Mac


No


No

SMS 2.0 and SMS 2003 Software Update Services (SUS) Feature Pack can use MBSA 1.2.1 for detection and therefore have the same limitation that is listed earlier in this bulletin related to programs that MBSA 1.2.1 does not detect.

For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool (SUIT), can be used by SMS to detect security updates. SMS SUIT uses the MBSA 1.2.1 engine for detection. For more information about SUIT, visit the following Microsoft Web site. For more information about the limitations of SUIT, 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 (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, 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.

For more detailed information, see Microsoft Knowledge Base Article 910723.
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Vulnerability Details

Excel Malformed IMDATA Record Vulnerability - CVE-2007-0027:

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

If a user is 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 IMDATA Record Vulnerability - CVE-2007-0027:


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 IMDATA Record Vulnerability - CVE-2007-0027:


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 IMDATA Record Vulnerability - CVE-2007-0027:

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

If a user is 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 impacted than users who operate with administrative user rights.

What causes the vulnerability?
Excel does not perform sufficient data validation when processing the contents of a file. When Excel opens a specially crafted Excel file and parses a malformed IMDATA 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 complete control of the affected system.

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 administrators allow users 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.

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 Record Vulnerability - CVE-2007-0028:

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

If a user is 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 Record Vulnerability - CVE-2007-0028:


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 Record Vulnerability - CVE-2007-0028:


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 Record Vulnerability - CVE-2007-0028:

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

If a user is 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 a file. When Excel opens a specially crafted Excel file and parses a malformed 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 complete control of the affected system.

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 administrators allow users 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.

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 String Vulnerability - CVE-2007-0029:

A remote code execution vulnerability exists in Microsoft Excel that could allow an attacker who successfully exploited this vulnerability to take complete control of the affected system.

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 String Vulnerability - CVE-2007-0029:


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 String Vulnerability - CVE-2007-0029:


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 String Vulnerability - CVE-2007-0029:

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

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 a file. When Excel opens a specially crafted Excel file and parses a malformed string 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 complete control of the affected system.

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 administrators allow users 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 string 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.

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 Column Record Vulnerability - CVE-2007-0030:

A remote code execution vulnerability exists in Microsoft Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed Column 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 Column Record Vulnerability - CVE-2007-0030:


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 Column Record Vulnerability - CVE-2007-0030:


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 Column Record Vulnerability - CVE-2007-0030:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Microsoft Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed Column 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 a file. When Excel opens a specially crafted Excel file and parses a malformed Column 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 complete control of the affected system.

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 administrators allow users 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 Column 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.

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 Palette Record Vulnerability - CVE-2007-0031:

A remote code execution vulnerability exists in Microsoft Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed Palette 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 Palette Record Vulnerability - CVE-2007-0031:


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 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 Palette Record Vulnerability - CVE-2007-0031:


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 Palette Record Vulnerability - CVE-2007-0031:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Microsoft Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed Palette 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 a file. When Excel opens a specially crafted Excel file and parses a malformed Palette 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 complete control of the affected system.

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 administrators allow users 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 Palette 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.

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:


Jeff Gennari of CERT for reporting the Excel Malformed IMDATA Record Vulnerability - CVE-2007-0027


Jie Ma of Fortinet Security Research Team for reporting the Excel Malformed Record Vulnerability - CVE-2007-0028


NSFocus Security Team for reporting the Excel Malformed String Vulnerability - CVE-2007-0029


Greg MacManus of iDefense Labs for reporting the Excel Malformed Column Record Vulnerability - CVE-2007-0030


Greg MacManus of iDefense Labs for reporting the Excel Malformed PALETTE Record Vulnerability - CVE-2007-0031


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 (January 9, 2007): Bulletin published.

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