CVE-2011-0103 in Excel
Summary
by MITRE
Microsoft Excel 2002 SP3 and 2003 SP3, Office 2004 and 2008 for Mac, and Open XML File Format Converter for Mac allow remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted record information in an Excel file, aka "Excel Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 11/02/2021
This vulnerability represents a critical memory corruption flaw affecting multiple versions of Microsoft Excel and related Office products across different platforms. The vulnerability stems from insufficient input validation within the Excel file parsing engine, specifically when processing crafted record information in Excel files. Attackers can exploit this weakness by creating malicious Excel files containing specially crafted data structures that trigger buffer overflows or other memory corruption conditions during file processing. The vulnerability affects Microsoft Excel 2002 SP3 and 2003 SP3 on Windows platforms, as well as Office 2004 and 2008 for Mac, along with the Open XML File Format Converter for Mac. This cross-platform impact demonstrates the widespread nature of the flaw within Microsoft's Office suite.
The technical exploitation of this vulnerability occurs when Excel attempts to parse malformed record data within Excel file formats such as .xls or .xlsx. When the application encounters crafted record information that exceeds expected buffer boundaries or violates memory allocation assumptions, it can lead to unpredictable behavior including arbitrary code execution or system crashes. The memory corruption typically manifests through stack or heap buffer overflows that can be leveraged by attackers to inject and execute malicious code within the context of the victim's session. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The vulnerability is particularly dangerous because it can be triggered through social engineering attacks where users unknowingly open malicious Excel files, making it a prime target for phishing campaigns and targeted attacks.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable full system compromise. When successfully exploited, attackers can execute arbitrary code with the privileges of the victim user, potentially leading to complete system takeover, data exfiltration, or establishment of persistent backdoors. The vulnerability's ability to affect both Windows and Mac platforms creates a broader attack surface, as organizations with mixed operating environments face increased risk. Security professionals should note that this vulnerability was particularly concerning because it affected older versions of Office that many organizations continued to use despite security updates, creating extended exposure windows. The memory corruption nature means that systems could experience crashes or instability, but more critically, the potential for code execution makes it a high-priority target for threat actors seeking to establish persistent access to networked environments.
Organizations should implement immediate mitigations including applying the relevant Microsoft security updates and patches released in response to this vulnerability. System administrators should consider implementing application whitelisting policies to restrict execution of Office applications from untrusted sources and deploy email filtering solutions to block potentially malicious Excel attachments. The vulnerability's classification under the ATT&CK framework would place it within the initial access and execution phases, specifically related to malicious file execution and exploitation of software vulnerabilities. Network segmentation and monitoring should be enhanced to detect unusual Office application behavior or attempts to access external resources. Regular security assessments should verify that all Office installations are updated to supported versions and that legacy systems are properly isolated. Additionally, user education programs should emphasize the importance of verifying file sources and avoiding opening suspicious Excel files, particularly those received via email or downloaded from untrusted websites.