CVE-2011-1988 in Office Compatibility Pack
Summary
by MITRE
Microsoft Excel 2003 SP3 and 2007 SP2; Excel in Office 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 parse records in Excel spreadsheets, which allows remote attackers to execute arbitrary code via a crafted spreadsheet, aka "Excel Heap Corruption Vulnerability."
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Analysis
by VulDB Data Team • 11/20/2021
The CVE-2011-1988 vulnerability represents a critical heap corruption flaw in Microsoft Excel applications across multiple versions and platforms. This vulnerability stems from improper parsing of records within Excel spreadsheet files, creating a condition where maliciously crafted spreadsheet documents can trigger memory corruption during the parsing process. The vulnerability affects a wide range of Microsoft Office products including Excel 2003 SP3 and 2007 SP2, Office 2004 and 2008 for Mac, Open XML File Format Converter for Mac, Excel Viewer SP2, and the Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP2. The flaw specifically manifests when the application attempts to process malformed or specially crafted records within Excel files, leading to unpredictable memory behavior that adversaries can exploit to execute arbitrary code on affected systems.
This vulnerability falls under the CWE-121 heap-based buffer overflow category, where the application fails to properly validate the size and structure of data records during spreadsheet parsing. The technical implementation involves the Excel application's failure to properly handle memory allocation when processing certain record types within the Excel file format, particularly affecting the heap memory management during file parsing operations. Attackers can craft malicious Excel files containing specially designed records that cause the application to allocate insufficient memory or overwrite adjacent memory regions, creating opportunities for code execution. The vulnerability is classified as a remote code execution flaw because attackers can deliver malicious spreadsheets through email attachments, web downloads, or file sharing mechanisms without requiring local access to the target system.
The operational impact of CVE-2011-1988 extends across enterprise environments where Microsoft Excel is widely deployed, potentially allowing attackers to gain full system control without user interaction. The vulnerability's exploitation typically requires the user to open the malicious spreadsheet file, making it particularly dangerous in targeted phishing campaigns or social engineering attacks. Security researchers have documented successful exploitation techniques that leverage the heap corruption to manipulate execution flow, potentially leading to privilege escalation or persistence mechanisms. The vulnerability affects organizations running various versions of Microsoft Office, making it a significant concern for enterprise security teams who must maintain multiple Office versions across their networks. Organizations with strict security policies may have already implemented mitigations such as disabling file format handling for untrusted sources or deploying email filtering solutions to prevent delivery of malicious spreadsheets.
Mitigation strategies for CVE-2011-1988 include immediate application of Microsoft security patches and updates, particularly the cumulative security updates released in response to this vulnerability. System administrators should implement application whitelisting policies that restrict execution of Excel files from untrusted sources, while also configuring email security solutions to scan for and block potentially malicious spreadsheet attachments. Network segmentation and endpoint protection measures can help limit the potential impact if exploitation occurs, while regular security awareness training can reduce the likelihood of users opening malicious files. The vulnerability's classification under the ATT&CK framework includes techniques such as T1204.002 (User Execution: Malicious File) and T1059.001 (Command and Scripting Interpreter: Visual Basic), highlighting the attack vectors and execution methods that adversaries can employ. Organizations should also consider deploying sandboxing solutions for processing untrusted Excel files and implementing strict file format validation policies to prevent exploitation attempts. The vulnerability underscores the importance of maintaining current security patches and demonstrates how legacy file format parsing issues can create persistent security risks in widely deployed office applications.