CVE-2011-0979 in Office Compatibility Pack
Summary
by MITRE
Microsoft Excel 2002 SP3, 2003 SP3, 2007 SP2, and 2010; Office 2004, 2008, and 2011 for Mac; Open XML File Format Converter for Mac; and Excel Viewer SP2 do not properly handle errors during the parsing of Office Art records in Excel spreadsheets, which allows remote attackers to execute arbitrary code via a malformed object record, related to a "stray reference," aka "Excel Linked List Corruption Vulnerability."
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Analysis
by VulDB Data Team • 10/17/2021
The vulnerability described in CVE-2011-0979 represents a critical memory corruption flaw affecting multiple versions of Microsoft Excel across different platforms including Windows and Mac operating systems. This vulnerability specifically targets the parsing mechanism of Office Art records within Excel spreadsheet files, creating a pathway for remote code execution through specially crafted malicious files. The flaw stems from inadequate error handling during the processing of Office Art objects, which are used to store graphical elements and formatting information within Excel documents.
The technical nature of this vulnerability can be classified under CWE-125, which describes "Out-of-bounds Read" conditions that occur when a program reads data from memory locations outside the intended buffer boundaries. The vulnerability manifests as a "stray reference" error during the parsing of Office Art records, where the Excel application fails to properly validate the structure and boundaries of linked data objects. When processing malformed object records, the application's memory management routines become compromised, leading to potential memory corruption that attackers can exploit to inject and execute arbitrary code with the privileges of the affected user.
From an operational perspective, this vulnerability poses significant risks to organizations relying on Microsoft Excel for data processing and analysis. Attackers can craft malicious Excel files that appear legitimate but contain corrupted Office Art records designed to trigger the memory corruption during normal spreadsheet opening operations. The vulnerability affects a wide range of Microsoft Office products including Excel 2002, 2003, 2007, 2010, as well as various Mac versions and the Open XML File Format Converter for Mac. This broad impact surface makes the vulnerability particularly dangerous as it can affect users across different Office versions and platforms. The attack vector is particularly concerning because it can be delivered through email attachments, web downloads, or file sharing mechanisms, making it a prime target for phishing campaigns and social engineering attacks.
The exploitability of this vulnerability aligns with ATT&CK technique T1203, which covers "Exploitation for Client Execution" where adversaries leverage software vulnerabilities to execute malicious code on target systems. The memory corruption aspect of this vulnerability also relates to ATT&CK technique T1068, "Exploitation for Privilege Escalation," as successful exploitation could potentially allow attackers to gain elevated privileges. The vulnerability's impact extends beyond simple code execution to include potential data compromise, system takeover, and lateral movement within network environments. Organizations should consider implementing defensive measures such as email filtering, application whitelisting, and user education to reduce exposure to this type of attack. The vulnerability's classification as a remote code execution flaw necessitates immediate patching of affected systems and implementation of network segmentation to limit potential attack spread.
Mitigation strategies should include immediate deployment of Microsoft security updates addressing this vulnerability, along with network-based protections such as email content filtering and web proxy configurations that can block suspicious Office file formats. Organizations should also consider implementing sandboxing mechanisms for Excel file processing and establishing strict file validation procedures for incoming documents. The vulnerability's nature as a memory corruption issue makes it particularly resistant to traditional antivirus solutions, emphasizing the importance of layered security approaches and proactive vulnerability management. Regular security assessments and penetration testing should be conducted to identify potential exploitation vectors and ensure that defensive measures remain effective against evolving attack techniques targeting similar memory corruption vulnerabilities.