CVE-2011-1277 in Excel
Summary
by MITRE
Microsoft Excel 2002 SP3, Office 2008 for Mac, and Open XML File Format Converter for Mac do not properly validate record information during parsing of Excel spreadsheets, which allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted spreadsheet, aka "Excel Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 11/09/2021
The vulnerability identified as CVE-2011-1277 represents a critical memory corruption flaw affecting Microsoft Excel 2002 SP3, Office 2008 for Mac, and the Open XML File Format Converter for Mac. This issue stems from inadequate validation of record information during the parsing process of Excel spreadsheet files, creating a pathway for malicious actors to exploit the software's handling of malformed data structures. The vulnerability operates at the core of spreadsheet parsing logic where the application fails to properly sanitize input parameters, leading to potential buffer overflows or memory corruption scenarios that can be leveraged for remote code execution.
The technical exploitation of this vulnerability occurs when a maliciously crafted Excel spreadsheet is opened by an affected application, triggering a parsing sequence that does not adequately validate the structure and content of records within the file format. This improper validation allows attackers to construct specific data patterns that cause the application to write beyond allocated memory boundaries or corrupt critical memory structures. The flaw manifests as a failure in input sanitization and boundary checking mechanisms that should normally prevent malformed data from causing system instability or unauthorized code execution. According to CWE classification, this vulnerability maps to CWE-125: "Out-of-bounds Read" and CWE-787: "Out-of-bounds Write," both of which are fundamental memory safety issues that enable arbitrary code execution through carefully crafted inputs.
From an operational perspective, the impact of CVE-2011-1277 extends beyond simple denial of service to encompass full system compromise potential. Remote attackers can leverage this vulnerability to execute arbitrary code on vulnerable systems with the privileges of the user running the affected Microsoft Office application. The memory corruption aspect creates opportunities for attackers to manipulate program execution flow, potentially leading to privilege escalation or persistent access within targeted environments. This vulnerability is particularly concerning in enterprise settings where Excel files are frequently shared and opened, as it can be exploited through social engineering campaigns or automated delivery mechanisms without requiring special user privileges or complex attack vectors.
The exploitation of this vulnerability aligns with several ATT&CK techniques including T1203: "Exploitation for Client Execution" and T1059: "Command and Scripting Interpreter," as attackers can leverage the memory corruption to gain code execution and subsequently deploy additional malicious payloads. Organizations utilizing affected versions of Microsoft Office should implement immediate mitigations including application whitelisting, email filtering to block suspicious Excel files, and user education regarding the risks of opening untrusted spreadsheet files. The recommended remediation involves applying Microsoft security updates and patches that address the underlying parsing validation issues. Additionally, network segmentation and monitoring for anomalous file access patterns can help detect potential exploitation attempts. System administrators should also consider disabling automatic opening of Excel files from untrusted sources and implementing strict file format validation policies to reduce the attack surface. The vulnerability demonstrates the critical importance of proper input validation and memory safety practices in office productivity applications that handle complex file formats and user-generated content.