CVE-2011-1987 in Office
Summary
by MITRE
Array index error in Microsoft Excel 2003 SP3 and 2007 SP2; Excel in Office 2007 SP2; Excel 2010 Gold and SP1; Excel in Office 2010 Gold and SP1; Office 2004, 2008, and 2011 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 allows remote attackers to execute arbitrary code via a crafted spreadsheet, aka "Excel Out of Bounds Array Indexing Vulnerability."
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Analysis
by VulDB Data Team • 11/20/2021
The vulnerability identified as CVE-2011-1987 represents a critical array index error in multiple versions of Microsoft Excel software across different platforms and office suites. This flaw manifests in Excel 2003 SP3 and 2007 SP2, Excel 2010 Gold and SP1, Office 2004, 2008, and 2011 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 vulnerability specifically impacts the handling of array indexing within spreadsheet processing mechanisms, creating a potential pathway for remote code execution through maliciously crafted spreadsheet files.
The technical nature of this vulnerability stems from improper bounds checking during array operations within Excel's parsing engine. When processing specially crafted spreadsheet files, the application fails to validate array indices properly, allowing an attacker to specify memory locations beyond the allocated array boundaries. This out-of-bounds array indexing flaw creates a condition where arbitrary memory can be accessed and modified, potentially enabling attackers to execute malicious code with the privileges of the user running the vulnerable Excel application. The vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a classic buffer overflow scenario that has been prevalent in software applications for decades.
The operational impact of this vulnerability extends beyond simple data corruption or application crashes, as it provides attackers with the capability to execute arbitrary code remotely. This means that simply opening a maliciously crafted Excel file could result in complete system compromise without requiring user interaction beyond the initial file opening. The vulnerability affects a wide range of Microsoft Office products, making it particularly dangerous as it can be exploited across multiple platforms and versions. Attackers could leverage this vulnerability to install malware, steal sensitive information, or establish persistent access to compromised systems. The remote exploitation capability makes this vulnerability particularly attractive to threat actors as it eliminates the need for physical access or additional attack vectors.
Organizations should implement multiple layers of defense to mitigate this vulnerability effectively. Immediate remediation through Microsoft security updates is essential, as Microsoft released patches specifically addressing this issue in their regular security bulletins. System administrators should also consider implementing application whitelisting policies that restrict the execution of untrusted spreadsheet files, particularly those from unknown sources. Network-based defenses such as email filtering and web proxies can help prevent the delivery of malicious files to end users. Additionally, user education regarding the dangers of opening untrusted spreadsheet files remains crucial. The vulnerability demonstrates the importance of maintaining up-to-date security patches and following the principle of least privilege in system configurations. From an ATT&CK framework perspective, this vulnerability maps to techniques involving execution through fileless methods and privilege escalation, making comprehensive security measures essential for protecting against exploitation attempts.