CVE-2008-4265 in Excel
Summary
by MITRE
Microsoft Office Excel 2000 SP3 allows remote attackers to execute arbitrary code via a crafted Excel spreadsheet that contains a malformed object, which triggers memory corruption during the loading of records from this spreadsheet, aka "File Format Parsing Vulnerability."
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Analysis
by VulDB Data Team • 08/21/2019
This vulnerability represents a critical file format parsing flaw in Microsoft Office Excel 2000 Service Pack 3 that enables remote code execution through maliciously crafted spreadsheet files. The vulnerability stems from insufficient input validation during the parsing of Excel file structures, specifically when processing malformed objects within spreadsheet records. Attackers can exploit this weakness by creating specially crafted Excel files that contain corrupted or malformed data structures which, when opened by an affected system, trigger memory corruption conditions. The flaw operates at the core parsing layer of the Excel application, where the software fails to properly validate the integrity of spreadsheet components before attempting to load and process them. This type of vulnerability falls under the CWE-125 vulnerability class, which encompasses out-of-bounds read errors that can lead to memory corruption and arbitrary code execution. The attack vector is particularly dangerous because it can be delivered through email attachments, web downloads, or any method that delivers an Excel file to a target system, making it a prime candidate for phishing campaigns and social engineering attacks. The vulnerability is classified as a remote code execution flaw under the ATT&CK framework's technique T1203, which involves gaining execution through file format vulnerabilities.
The technical implementation of this vulnerability exploits the way Excel 2000 SP3 handles record structures within Excel files, particularly when encountering malformed or corrupted object references in the spreadsheet format. When the application attempts to parse these invalid records, it accesses memory locations beyond the allocated buffer space, leading to memory corruption that can be leveraged to execute arbitrary code with the privileges of the user running the application. The memory corruption occurs during the normal loading sequence of Excel files, making detection difficult as the malicious behavior is indistinguishable from legitimate file processing. This vulnerability is particularly concerning because Excel 2000 SP3 was widely deployed in enterprise environments, and the exploitation mechanism requires no user interaction beyond opening the malicious file, making it highly effective for mass deployment attacks. The flaw demonstrates a classic buffer overflow condition where the application does not properly validate the size or structure of data elements before processing them, allowing attackers to craft inputs that exceed expected boundaries.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass full system compromise capabilities when combined with other exploitation techniques. An attacker who successfully exploits this vulnerability can gain complete control over the target system, potentially leading to data exfiltration, persistence mechanisms, and further network reconnaissance. The vulnerability affects not just individual users but entire organizations that rely on Excel 2000 SP3 for business operations, as a single compromised file can lead to widespread system compromise. Organizations running this legacy software face significant risk since Microsoft has long since ended support for Excel 2000, meaning no security updates or patches are available to address the underlying flaw. The vulnerability's exploitation requires minimal technical skill, making it attractive to both sophisticated threat actors and less experienced attackers. Security professionals should consider this vulnerability as part of a broader attack surface assessment, particularly in environments where legacy software remains in use. The impact is compounded by the fact that many organizations may not be aware of their continued use of vulnerable software, creating blind spots in their security posture.
Mitigation strategies for this vulnerability must address both immediate protection and long-term remediation. Organizations should implement immediate network-level protections including email filtering, web proxy restrictions, and file type blocking for Excel files from untrusted sources. The most effective long-term solution involves upgrading to supported versions of Microsoft Office that have addressed this vulnerability through proper input validation and memory management. Security teams should also consider implementing application whitelisting policies that prevent execution of legacy applications like Excel 2000 SP3 on production systems. Network segmentation and user privilege controls can help limit the potential damage if exploitation occurs, while regular vulnerability assessments should identify other legacy software components that may present similar risks. The ATT&CK framework suggests implementing detection capabilities that monitor for unusual file processing behaviors, particularly around Excel file parsing operations, as a proactive defense mechanism. Additionally, organizations should maintain comprehensive incident response procedures that account for file format vulnerabilities, ensuring rapid identification and containment of exploitation attempts. Given the age of Excel 2000 SP3, the most effective mitigation remains complete software retirement and replacement with modern, supported versions that include robust security features and regular patch management processes.