CVE-2011-0097 in Excel
Summary
by MITRE
Integer underflow in Microsoft Excel 2002 SP3, 2003 SP3, 2007 SP2, and 2010; 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 allows remote attackers to execute arbitrary code via a crafted 400h substream in an Excel file, which triggers a stack-based buffer overflow, aka "Excel Integer Overrun Vulnerability."
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Analysis
by VulDB Data Team • 11/02/2021
The CVE-2011-0097 vulnerability represents a critical integer underflow flaw in multiple Microsoft Office versions that enables remote code execution through maliciously crafted Excel files. This vulnerability specifically affects Microsoft Excel 2002 SP3, 2003 SP3, 2007 SP2, 2010, 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 manifests when processing a crafted 400h substream within Excel files, creating a stack-based buffer overflow condition that can be exploited by remote attackers to execute arbitrary code on affected systems.
The technical implementation of this vulnerability stems from improper input validation within Microsoft Excel's file parsing routines. When the application encounters a specially crafted 400h substream in an Excel file, it fails to properly validate integer values during the processing of file structures. This integer underflow condition causes the application to allocate insufficient memory for buffer operations, leading to a stack-based buffer overflow. The vulnerability is classified under CWE-190 as an integer overflow or wraparound, while the specific execution mechanism aligns with CWE-121 stack-based buffer overflow patterns. The ATT&CK framework categorizes this as a remote code execution technique leveraging software exploitation, specifically targeting application security flaws in Microsoft Office applications.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass potential system compromise and data theft. Attackers can leverage this vulnerability to gain unauthorized access to affected systems, potentially escalating privileges and establishing persistent backdoors. The vulnerability affects a broad range of Microsoft Office products, making it particularly dangerous as organizations often maintain multiple versions across their infrastructure. The exploit requires minimal user interaction beyond opening a malicious Excel file, making it suitable for phishing campaigns and social engineering attacks. Additionally, the vulnerability's presence in compatibility packs and viewer applications means that even systems without the primary Office suite can be at risk when processing Excel files.
Mitigation strategies for CVE-2011-0097 should prioritize immediate patching of all affected Microsoft Office versions through Microsoft Security Bulletins MS11-014 and related updates. Organizations should implement strict file validation policies, including disabling macro execution and restricting Excel file processing in high-risk environments. Network-based mitigations such as email filtering and web application firewalls can help prevent delivery of malicious Excel files. Security awareness training should emphasize the dangers of opening unexpected Excel files, particularly from untrusted sources. System hardening measures including disabling unnecessary Office features, implementing least privilege access controls, and maintaining current antivirus signatures are essential defensive measures. The vulnerability also highlights the importance of regular security assessments and vulnerability management processes to identify and remediate similar issues before they can be exploited in the wild.