CVE-2010-1249 in Excel
Summary
by MITRE
Buffer overflow in Microsoft Office Excel 2002 SP3, Office 2004 for Mac, Office 2008 for Mac, and Open XML File Format Converter for Mac allows remote attackers to execute arbitrary code via an Excel file with a malformed ExternName (0x23) record, aka "Excel Memory Corruption Vulnerability," a different vulnerability than CVE-2010-0823 and CVE-2010-1247.
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Analysis
by VulDB Data Team • 09/15/2021
This vulnerability represents a critical buffer overflow flaw in Microsoft Office Excel products that affects multiple platform versions including Excel 2002 SP3, Office 2004 for Mac, Office 2008 for Mac, and the Open XML File Format Converter for Mac. The vulnerability specifically manifests when processing Excel files containing a malformed ExternName record with the identifier 0x23, creating a memory corruption condition that can be exploited by remote attackers to execute arbitrary code on affected systems. The flaw stems from insufficient input validation and bounds checking within the Excel file parsing mechanism, particularly when handling external name references in workbook files. This vulnerability is distinct from other related issues such as CVE-2010-0823 and CVE-2010-1247, indicating separate code paths and exploitation vectors within the Excel application's handling of different file structures.
The technical implementation of this buffer overflow occurs during the parsing of Excel file format records, specifically when the application encounters the ExternName record type 0x23 which contains external name information used for linking external data sources. When an attacker crafts a malicious Excel file with improperly formatted ExternName records, the application fails to properly validate the record length and data boundaries, leading to memory corruption when the buffer is overwritten beyond its allocated size. This memory corruption typically manifests through stack or heap corruption that can be leveraged to redirect program execution flow, allowing attackers to inject and execute malicious code with the privileges of the affected user. The vulnerability is particularly dangerous because it can be triggered through simple file opening operations, making it an attractive target for phishing attacks and malicious file distribution campaigns.
The operational impact of this vulnerability extends beyond simple code execution to encompass significant security implications for enterprise environments and individual users alike. Attackers can leverage this vulnerability to gain unauthorized access to systems, escalate privileges, and potentially establish persistent backdoors through the execution of malicious payloads. The cross-platform nature of the vulnerability affects both Windows and Mac versions of Microsoft Office, increasing the potential attack surface and making it particularly concerning for organizations with mixed operating system environments. The vulnerability's ability to be triggered remotely through email attachments or web downloads makes it a prime candidate for widespread exploitation, potentially leading to data breaches, system compromise, and unauthorized access to sensitive corporate or personal information. Organizations utilizing affected Office versions face heightened risk of targeted attacks and supply chain compromises.
Mitigation strategies for this vulnerability should encompass multiple layers of defense including immediate patch deployment from Microsoft, as well as network-level protections such as email filtering and file type restrictions. Security administrators should implement strict file validation policies that prevent execution of potentially malicious Excel files from untrusted sources, while also monitoring for suspicious file access patterns that might indicate exploitation attempts. The vulnerability aligns with attack patterns documented in the mitre attack framework under techniques related to malicious file execution and privilege escalation, specifically mapping to tactics such as execution and persistence. Organizations should also consider implementing application whitelisting policies to restrict which Excel versions can be executed and ensure that users are not automatically opening potentially malicious files. Regular security awareness training for end users remains crucial as social engineering aspects of exploitation often involve convincing users to open malicious attachments that trigger this vulnerability through normal office application usage patterns.