Microsoft has re-released a security bulletin and updated software to address the Microsoft Office Excel FNGROUPNAME record arbitrary code execution vulnerability.
Microsoft Office Excel contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code.
The vulnerability is due to unsafe memory operations performed when opening Excel documents that contain a malformed FNGROUPNAME record. An unauthenticated, remote attacker could exploit the vulnerability by convincing a user to view a malicious document. If the user views the document, the attacker could execute arbitrary code with the privileges of the user.
Microsoft has confirmed this vulnerability in a security bulletin and released software updates.
Microsoft Office Excel 2007 SP2 and prior, Microsoft Office Excel 2003 SP3 and prior, and Office for Mac 2004 are vulnerable.
Exploitation is difficult because the memory data is fixed, and an attacker must have access to the uninitialized memory before exploiting this code.
Attackers cannot directly exploit this vulnerability and instead rely on user interaction to accomplish an exploit. The attacker must persuade a user to view a malicious document. Attackers may provide documents to users as attachments to e-mail messages or as links in e-mail or instant messages that direct users to documents posted on websites. If an exploit is successful, the attacker could execute code with the privileges as the user.
Microsoft has re-released a security bulletin at the following link: MS10-017
An unauthenticated, remote attacker could exploit this vulnerability to execute arbitrary code with the privileges of the user. If that user holds elevated privileges, the attacker could completely compromise the system.
The vulnerability is due to improper initialization of a local function variable during the processing of FNGROUPNAME records. The processing of such records could cause Excel to access previously removed or uninitialized memory areas.
An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to view a malicious Excel document that is designed to cause the application to parse FNGROUPNAME records without initializing a specific stack variable. When opened, the document could trigger a stack-based overflow that the attacker could use to execute arbitrary code with the privileges of the user.
Administrators are advised to apply the available software updates.
Users are advised not to open unsolicited e-mail attachments. Users should verify that attachments are safe before opening them.
Users are advised to run applications with the least necessary privileges.
Users may consider applying the Microsoft Office Isolated Conversion Environment (MOICE) to safely open Excel files from suspicious or unrecognized sources on systems that are running Microsoft Office 2003 or Office 2007.
Administrators may consider using the Microsoft Baseline Security Analyzer (MBSA) scan tool to identify common security misconfigurations and missing security updates on system endpoints.
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Version 2, March 10, 2010, 1:01 PM: Additional technical information is available to describe the Microsoft Office Excel FNGROUPNAME record arbitrary code execution vulnerability.
Version 1, March 9, 2009, 1:56 PM: Microsoft Office Excel contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code with the privileges of the user. Updates are available.
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