CVE-2006-0020 in Internet Explorer
Summary
by MITRE
An unspecified Microsoft WMF parsing application, as used in Internet Explorer 5.01 SP4 on Windows 2000 SP4, and 5.5 SP2 on Windows Millennium, and possibly other versions, allows attackers to cause a denial of service (crash) and possibly execute code via a crafted WMF file with a manipulated WMF header size, possibly involving an integer overflow, a different vulnerability than CVE-2005-4560, and aka "WMF Image Parsing Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 06/25/2025
The vulnerability described in CVE-2006-0020 represents a critical memory corruption issue within Microsoft Windows Metafile (WMF) parsing functionality that affected multiple versions of Internet Explorer across different Windows operating systems. This flaw specifically targeted the way Internet Explorer processed WMF image files, which are vector graphics formats commonly used in web applications and document processing. The vulnerability emerged from the improper handling of WMF header structures, particularly when the header size field contained manipulated values that could trigger unexpected behavior in the parsing routine.
The technical implementation of this vulnerability involved an integer overflow condition within the WMF parsing code that occurred when processing specially crafted WMF files. When Internet Explorer encountered a malformed WMF header with an oversized size field, the parsing algorithm would attempt to allocate memory based on the manipulated header size value. This integer overflow could result in insufficient memory allocation or memory corruption, creating conditions where attackers could manipulate the program execution flow. The vulnerability was classified under CWE-129 as an insufficient validation of length of a field, while also demonstrating characteristics of CWE-190 related to integer overflow and CWE-787 related to out-of-bounds write operations.
The operational impact of this vulnerability was significant as it provided attackers with a potential pathway for both denial of service and remote code execution against affected systems. When exploited, the vulnerability could cause Internet Explorer to crash and terminate unexpectedly, leading to a denial of service condition that disrupted user productivity and web browsing operations. More critically, the memory corruption conditions created by the integer overflow could potentially be leveraged to execute arbitrary code with the privileges of the affected user, making this a severe security concern for enterprise environments and individual users alike. The attack vector was particularly dangerous as it could be delivered through web pages, email attachments, or other methods that would cause Internet Explorer to process WMF images automatically.
This vulnerability was distinct from CVE-2005-4560, which addressed different aspects of WMF parsing flaws, indicating that Microsoft was dealing with multiple related issues within their graphics processing libraries. The attack scenario typically involved luring users to visit malicious websites containing specially crafted WMF images or sending email attachments with manipulated WMF content that would trigger the vulnerable parsing code when displayed or processed by Internet Explorer. The affected configurations included Internet Explorer 5.01 SP4 on Windows 2000 SP4 and Internet Explorer 5.5 SP2 on Windows Millennium Edition, though the vulnerability may have extended to other versions of the affected software. Organizations implementing mitigation strategies needed to consider the broader implications for their security posture, as this vulnerability demonstrated the persistent risks associated with legacy software components and the challenges of maintaining secure code handling for graphics processing functions.
Microsoft addressed this vulnerability through security updates that corrected the WMF parsing logic to properly validate header size fields and prevent integer overflow conditions. The remediation efforts were aligned with defensive programming practices that emphasize input validation and memory safety mechanisms. Security professionals should note that this vulnerability exemplifies the importance of proper bounds checking in graphics processing libraries and the potential for seemingly benign file format parsing to create severe security risks. The incident highlighted the need for comprehensive security testing of multimedia processing components and underscored the ongoing challenge of securing legacy applications that continue to be deployed in enterprise environments. Organizations were advised to implement immediate patches, deploy web content filtering solutions, and educate users about the risks of opening untrusted graphics files to mitigate exposure to this and similar vulnerabilities in their computing environments.