Microsoft Security Bulletin MS07-023 Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (934233)

Microsoft Security Bulletin MS07-023
Vulnerabilities in Microsoft Excel Could Allow Remote Code Execution (934233)
Published: May 8, 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 details.

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:
•

Microsoft Office 2000 Service Pack 3
•

Microsoft Excel 2000 - Download the update (KB934447)
•

Microsoft Office XP Service Pack 3
•

Microsoft Excel 2002 - Download the update (KB934453)
•

Microsoft Office 2003 Service Pack 2
•

Microsoft Excel 2003 - Download the update (KB933666)
•

Microsoft Excel 2003 Viewer - Download the update (KB934445)
•

2007 Microsoft Office System
•

Microsoft Office Excel 2007 - Download the update (KB934670)
•

Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats - Download the update (KB933688)
•

Microsoft Office 2004 for Mac - Download the update (KB936749)

Non-Affected Software:
•

Microsoft Works Suites:
•

Microsoft Works Suite 2004
•

Microsoft Works Suite 2005
•

Microsoft Works Suite 2006

The software in this list has been tested to determine whether the versions are affected. Other versions are either past their support life cycle or are not 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.

We recommend that customers apply the update immediately.

Severity Ratings and Vulnerability Identifiers:
Vulnerability Identifiers Impact of Vulnerability Microsoft Excel 2000 Service Pack 3 Microsoft Excel 2002 Service Pack 3 Microsoft Excel 2003 Service Pack 2 Microsoft Excel 2003 Viewer Microsoft Office Excel 2007 and Microsoft Office Compatibility Pack Microsoft Office 2004 for Mac

Excel BIFF Record Vulnerability - CVE-2007-0215

Remote Code Execution

Critical

Important

Important

Important

None

None

Excel Set Font Vulnerability - CVE-2007-1203

Remote Code Execution

Critical

Important

Important

Important

Important

Important

Excel Filter Record Vulnerability CVE-2007-1214

Remote Code Execution

Critical

Important

Important

Important

None

Important

Aggregate Severity of All Vulnerabilities

Critical

Important

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.
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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 software is listed in the following table.
Bulletin ID Microsoft Excel 2000 Service Pack 3 Microsoft Excel 2002 Service Pack 3 Microsoft Excel 2003 Service Pack 2 and the Microsoft Excel 2003 Viewer Microsoft Office Excel 2007 and the Microsoft Office Compatibility Pack Microsoft Office 2004 for Mac

MS07-002

Replaced

Replaced

Replaced

Not applicable

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 2.0.1

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 2003 Viewer

Yes

Yes

Microsoft Office Excel 2007

Yes

Yes

Microsoft Office Compatibility Pack

Yes

Yes

Microsoft Office 2004 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 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, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.

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

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 2003 Viewer

Yes

Yes

Microsoft Office Excel 2007

Yes

Yes

Microsoft Office Compatibility Pack

Yes

Yes

Microsoft Office 2004 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.

Note If you have used an Administrative Installation Point (AIP) for deploying Office 2000, Office XP or Office 2003, you may not be able to deploy the update using SMS if you have updated the AIP from the original baseline.
•

For more information about how to change the source for a client computer from an updated administrative installation point to an Office 2000 original baseline source or Service Pack 3 (SP3), see Microsoft Knowledge Base Article 932889.
•

For more information on how to change the source for a client computer from an updated administrative installation point to an Office XP original baseline source or Service Pack 3 (SP3), see Microsoft Knowledge Base Article 922665.
•

For more information about how to change the source for a client computer from an updated administrative installation point to an Office 2003 original baseline source or Service Pack 2 (SP2), see Microsoft Knowledge Base Article 902349.

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.
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Vulnerability Details

Excel BIFF Record Vulnerability - CVE-2007-0215:

A remote code execution vulnerability exists in the way Excel handles files with malformed BIFF records. Such a file might be included in an e-mail attachment or hosted on a malicious Web site. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

Mitigating Factors for Excel BIFF Record Vulnerability - CVE-2007-0215:
•

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 Office 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 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 BIFF Record Vulnerability - CVE-2007-0215:

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 BIFF Record Vulnerability - CVE-2007-0215:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in the way Excel handles Excel files with malformed BIFF records. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

What causes the vulnerability?
The vulnerability is caused by Excel not correctly handling Excel files with malformed BIFF records, which could result in the corruption of 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 cause arbitrary code to run with the privileges of the user who opened the file.

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 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.

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 handles malformed BIFF records.

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 Set Font Vulnerability - CVE-2007-1203:

A remote code execution vulnerability exists in the way Excel handles Excel files with specially crafted set font values. Such a file might be included in an e-mail attachment or hosted on a malicious Web site. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

Mitigating Factors for Excel Set Font Vulnerability - CVE-2007-1203:
•

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 Office 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 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 Set Font Vulnerability - CVE-2007-1203:

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 Set Font Vulnerability - CVE-2007-1203:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in the way Excel handles Excel files with specially crafted set font values. Such a file might be included in an e-mail attachment or hosted on a malicious Web site. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

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?
The vulnerability is caused by Excel not correctly handling Excel files with a specially crafted set font value, which will results in the corruption of memory.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could cause arbitrary code to run with the privileges of the user who opened the file.

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 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. An attacker would have no way to force users to visit a specially crafted Web site and open an Excel file. 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.

What systems are primarily at risk from the vulnerability?
Workstations and terminal servers that have Microsoft Excel installed 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 handles set font values 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 Filter Record Vulnerability CVE-2007-1214:

A remote code execution vulnerability exists in the way Excel handles Excel files with specially crafted filter records. Such a file might be included in an e-mail attachment or hosted on a malicious Web site. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

Mitigating Factors for Excel Filter Record Vulnerability CVE-2007-1214:
•

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 Office 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 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 Filter Record Vulnerability CVE-2007-1214:

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 Filter Record Vulnerability CVE-2007-1214:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in the way Excel handles Excel files with specially crafted values. Such a file might be included in an e-mail attachment or hosted on a malicious Web site. An attacker could exploit the vulnerability by constructing a specially crafted Excel file that could allow remote code execution.

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 Excel file with a specially crafted filter record, it may corrupt 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 cause arbitrary code to run with the privileges of the user who opened the file.

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 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.

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 validates filter records 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.

Acknowledgments

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

Manuel Santamarina Suarez, working with TippingPoint and the Zero Day Initiative, for reporting the Excel BIFF Record Vulnerability (CVE-2007-0215)
•

Greg MacManus of iDefense Labs for reporting the Excel Filter Record Vulnerability (CVE-2007-1214)

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 (May 8, 2007): Bulletin published.