CVE-2010-0263 in Office
Summary
by MITRE
Microsoft Office Excel 2007 SP1 and SP2; Office 2008 for Mac; Open XML File Format Converter for Mac; Office Excel Viewer SP1 and SP2; Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats SP1 and SP2; and Office SharePoint Server 2007 SP1 and SP2 do not validate ZIP headers during decompression of Open XML (.XLSX) documents, which allows remote attackers to execute arbitrary code via a crafted document that triggers access to uninitialized memory locations, aka "Microsoft Office Excel XLSX File Parsing Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 05/02/2026
This vulnerability resides in Microsoft Office applications that process Open XML document formats, specifically affecting Excel 2007 SP1 and SP2, Office 2008 for Mac, the Open XML File Format Converter for Mac, Excel Viewer SP1 and SP2, the Office Compatibility Pack for Word, Excel, and PowerPoint 2007 file formats SP1 and SP2, and Office SharePoint Server 2007 SP1 and SP2. The flaw manifests during the decompression process of .XLSX files when the applications fail to properly validate ZIP headers before extracting file contents. This validation gap creates a condition where maliciously crafted ZIP archives within Excel documents can bypass normal security checks and trigger code execution.
The technical mechanism behind this vulnerability involves the improper handling of compressed data structures within the Open XML format. When Excel encounters an .XLSX file, it attempts to decompress the embedded ZIP archive to access the document components. However, the application does not adequately verify the integrity of the ZIP headers before proceeding with decompression operations. This oversight allows attackers to craft malicious documents containing specially formatted ZIP headers that cause the decompression routine to access memory locations that have not been properly initialized, leading to potential memory corruption and arbitrary code execution. The vulnerability is classified as a buffer over-read condition under CWE-125 and represents a classic example of improper input validation in decompression routines.
The operational impact of this vulnerability is significant as it enables remote code execution attacks without requiring user interaction beyond opening a malicious document. Attackers can exploit this weakness by embedding crafted ZIP headers within seemingly legitimate Excel files, making the attack vector particularly dangerous in enterprise environments where users frequently open documents from external sources. The vulnerability affects multiple Microsoft Office products across different platforms, amplifying its potential attack surface and making it a preferred target for cybercriminals seeking to compromise office environments. This type of vulnerability aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for code execution.
Mitigation strategies for this vulnerability require immediate application of Microsoft security updates and patches that address the ZIP header validation issue. Organizations should implement strict document filtering policies that prevent opening of untrusted .XLSX files, particularly those received via email or downloaded from unverified sources. Network-based security controls such as email filtering and web proxies can help reduce the risk of exploitation by blocking malicious attachments before they reach end users. Additionally, implementing application whitelisting controls that restrict execution of unauthorized Office applications can provide an additional layer of defense. Regular security awareness training for users to recognize suspicious document attachments and understand the risks associated with opening files from unknown sources remains essential for comprehensive protection against this type of vulnerability.