Additional technical information is available related to the Office Excel XLSX file parsing vulnerability.
Microsoft Office Excel contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code.
The vulnerability is due to errors in processing malformed Microsoft Office Open XML Spreadsheet (.xlsx) files. The XLSX format was introduced in Office 2007, although it can be read by earlier versions of Office through the Microsoft Office Compatibility Pack. An unauthenticated, remote attacker could exploit the vulnerability by convincing a user to view a malicious document. If the user opens the file, 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.
The following Microsoft products are affected:
Office Excel 2007 SP2 and prior
Office Excel Viewer 2007 SP2 and prior
Office 2008 for Mac
Open XML File Format Converter for Mac
Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP2 and prior
Sharepoint Portal Server 2007 (32-bit) SP2 and prior
Sharepoint Portal Server 2007 (64-bit) SP2 and prior
In order to exploit the vulnerability, an attacker must be able to convince a user to view a malicious document within Excel. The attacker may provide documents to the user as an attachment to an e-mail message or by providing links in e-mail or instant messages. An attacker may also use social engineering techniques in an attempt to convince users to open a provided document.
An exploit could allow the attacker to execute arbitrary code with the privileges of the user. Systems that grant users elevated privileges are at greatest risk, as any code execution would occur in a privileged security context, potentially allowing the attacker to take complete control over the system.
Microsoft has 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 execute arbitrary code resulting in a complete compromise.
The vulnerability is due to insufficient validation of document archive headers when the affected software processes Microsoft .xlsx files. The .xlsx file is a ZIP archive consisting of files that define the Open XML document. An unauthenticated, remote attacker could exploit this vulnerability by including a malicious .xml file in the .xlsx file archive and then convincing a user to view the malicious document. The processing of malformed archive header fields could result in an uninitialized memory pointer, which an 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 privileges possible.
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 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.
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