CVE-2002-0618 in Excel
Summary
by MITRE
The Macro Security Model in Microsoft Excel 2000 and 2002 for Windows allows remote attackers to execute code in the Local Computer zone by embedding HTML scripts within an Excel workbook that contains an XSL stylesheet, aka "Excel XSL Stylesheet Script Execution".
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Analysis
by VulDB Data Team • 12/30/2024
The vulnerability described in CVE-2002-0618 represents a critical security flaw in Microsoft Excel 2000 and 2002 that exploited the macro security model to enable remote code execution. This vulnerability specifically targeted the way Excel handled XSL stylesheets within workbooks, creating a dangerous intersection between spreadsheet functionality and web-based scripting capabilities. The flaw allowed attackers to embed malicious HTML scripts within Excel workbooks that contained XSL stylesheet references, effectively bypassing the security boundaries that should have prevented execution of untrusted code in the Local Computer zone.
The technical mechanism behind this vulnerability involved the improper handling of XSL (Extensible Stylesheet Language) transformations within Excel documents. When an Excel workbook containing an XSL stylesheet was opened, the application would process the stylesheet and execute embedded scripts without proper security validation. This occurred because the macro security model in Excel 2000 and 2002 failed to adequately distinguish between trusted and untrusted stylesheet content, allowing HTML-based scripts to be interpreted and executed within the context of the Local Computer zone. The vulnerability leveraged the fact that XSL stylesheets could contain script references that would be processed by the underlying XML parser, which in turn could trigger code execution in the context of the user's privileges.
The operational impact of this vulnerability was severe and far-reaching, as it enabled attackers to execute arbitrary code on vulnerable systems without requiring user interaction beyond opening a malicious Excel file. The Local Computer zone typically grants higher privileges to content, making this vulnerability particularly dangerous because it could allow attackers to bypass standard security restrictions that protect against malicious code execution. This flaw effectively created a backdoor through which attackers could deploy malware, steal sensitive data, or establish persistent access to compromised systems. The vulnerability was especially concerning because Excel was widely used in corporate environments, making the attack surface extensive and the potential damage significant.
Mitigation strategies for this vulnerability required immediate action from organizations, including applying Microsoft security patches that addressed the XSL stylesheet processing behavior in Excel. System administrators needed to implement strict file validation policies and disable the automatic execution of XSL transformations in Excel environments. The recommended approach involved configuring Excel to disable external references and limiting the execution of embedded scripts within workbooks. Organizations should have also considered implementing application control measures and network-level filtering to prevent the delivery of malicious Excel files containing embedded XSL stylesheets. This vulnerability highlighted the importance of proper input validation and the need for robust security models that could handle complex document formats without creating execution paths for malicious code.
This vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code" and represents a classic example of how complex document processing can create security risks when proper validation and isolation mechanisms are absent. The attack pattern described in the vulnerability corresponds to techniques categorized under ATT&CK matrix tactic TA0002 (Execution) and technique T1059.005 (Command and Scripting Interpreter), specifically targeting the execution of scripts within spreadsheet applications. The flaw also demonstrates characteristics of privilege escalation vulnerabilities, as it allowed code execution with the privileges of the user running Excel, potentially leading to full system compromise when combined with other exploitation techniques.