CVE-2011-1272 in Excel
Summary
by MITRE
Microsoft Excel 2002 SP3, 2003 SP3, and 2007 SP2; Office 2004 and 2008 for Mac; Open XML File Format Converter for Mac; Excel Viewer SP2; and Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP2 do not properly validate record structures during parsing of Excel spreadsheets, which allows remote attackers to execute arbitrary code via a crafted spreadsheet, aka "Excel Insufficient Record Validation Vulnerability."
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Analysis
by VulDB Data Team • 03/19/2021
The Excel Insufficient Record Validation Vulnerability represents a critical parsing flaw that affects multiple versions of Microsoft Excel and related Office applications across different platforms. This vulnerability stems from inadequate validation of record structures within Excel spreadsheet files during the parsing process, creating a pathway for malicious actors to exploit the software's file handling mechanisms. The flaw specifically targets the way these applications process structured data within Excel files, particularly when encountering malformed or specially crafted records that fall outside normal parsing parameters.
The technical exploitation of this vulnerability occurs through the manipulation of record structures within Excel files, where attackers craft malicious spreadsheets containing specially formatted data that triggers improper validation handling. When affected applications attempt to parse these malformed records, the validation mechanisms fail to properly identify and reject the malicious content, allowing execution of arbitrary code on the target system. This type of vulnerability falls under the CWE-129 category of "Improper Validation of Array Index" and represents a classic buffer overflow scenario where insufficient bounds checking enables code execution. The vulnerability is particularly dangerous because it can be triggered through normal file opening operations, making it accessible to attackers who simply need to entice victims to open a malicious spreadsheet.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise across multiple platforms including windows and mac operating systems. Attackers can leverage this vulnerability to gain unauthorized access to systems, escalate privileges, and potentially establish persistent backdoors within corporate networks. The widespread adoption of Excel across business environments makes this vulnerability particularly attractive to threat actors, as it can be delivered through email attachments, web downloads, or other common attack vectors. This vulnerability directly aligns with the ATT&CK technique T1059.005 for Command and Scripting Interpreter, as exploitation typically involves executing malicious code through the targeted application's process. The impact is further amplified by the fact that these affected versions include widely used Office applications that are frequently opened by end users, creating numerous potential entry points for attackers.
Mitigation strategies for this vulnerability require immediate patching of all affected Office versions, as Microsoft has released security updates specifically addressing the record validation issues in these applications. Organizations should implement strict file validation policies, including the use of file type restrictions and content scanning mechanisms to prevent execution of potentially malicious spreadsheets. Network segmentation and application whitelisting can provide additional defense layers by limiting the execution of untrusted Office files. Security awareness training for end users remains crucial to prevent social engineering attacks that might deliver malicious Excel files through phishing campaigns. Regular vulnerability assessments and penetration testing should focus on identifying and addressing similar parsing vulnerabilities in other Office applications and third-party software that may exhibit similar validation flaws. The vulnerability also highlights the importance of proper input validation and robust error handling in software development practices, emphasizing the need for comprehensive security testing during the software development lifecycle to prevent such issues from reaching production environments.