CVE-2006-4868 in Internet Explorer
Summary
by MITRE
Stack-based buffer overflow in the Vector Graphics Rendering engine (vgx.dll), as used in Microsoft Outlook and Internet Explorer 6.0 on Windows XP SP2, and possibly other versions, allows remote attackers to execute arbitrary code via a Vector Markup Language (VML) file with a long fill parameter within a rect tag.
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Analysis
by VulDB Data Team • 06/16/2025
The vulnerability identified as CVE-2006-4868 represents a critical stack-based buffer overflow within Microsoft's Vector Graphics Rendering engine component known as vgx.dll. This flaw specifically affects Microsoft Outlook and Internet Explorer 6.0 running on Windows XP Service Pack 2 systems, though it may potentially impact other versions of the affected software. The vulnerability stems from inadequate input validation within the VML processing functionality, creating an exploitable condition that can be triggered through maliciously crafted VML files. The flaw manifests when a VML file contains an excessively long fill parameter within a rect tag element, which causes the rendering engine to write beyond the allocated memory buffer on the stack.
From a technical perspective, this vulnerability operates through a classic stack buffer overflow mechanism where the VML parser fails to properly bounds-check the length of the fill attribute parameter. When processing the rect element with an oversized fill parameter, the rendering engine attempts to store data beyond the intended buffer boundaries, potentially overwriting adjacent stack memory locations including return addresses and function parameters. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that allows attackers to manipulate program execution flow. The vulnerability is particularly concerning because it enables remote code execution, meaning an attacker can deliver malicious VML content through web pages, email attachments, or other network-delivered content without requiring user interaction beyond viewing the content.
The operational impact of CVE-2006-4868 is severe given the widespread deployment of Internet Explorer 6.0 and Microsoft Outlook on Windows XP systems during the time of the vulnerability's discovery. Attackers could exploit this weakness by hosting malicious VML content on web servers or embedding it in email messages that, when processed by the vulnerable applications, would execute arbitrary code with the privileges of the affected user. The attack surface extends beyond simple web browsing to include email client processing, making it particularly dangerous in enterprise environments where email remains a primary attack vector. This vulnerability aligns with ATT&CK technique T1203 Exploitation for Client Execution, as it leverages client-side applications to achieve code execution. The exploitation typically requires no user interaction beyond viewing the malicious content, making it a prime target for automated attacks and drive-by downloads that could compromise large numbers of systems.
Mitigation strategies for this vulnerability involve multiple layers of defense as recommended by industry best practices. Microsoft released security patches through Windows Update that addressed the buffer overflow in vgx.dll, and system administrators should ensure all affected systems receive the appropriate security updates. Network administrators should implement content filtering solutions that can detect and block malicious VML content, particularly in email gateways and web proxies. Disabling the processing of VML content in browsers and email clients when not required provides an additional protective measure. Organizations should also consider implementing application whitelisting policies that restrict execution of unsigned or untrusted code. The vulnerability highlights the importance of proper input validation and memory safety practices in software development, as outlined in the OWASP Top Ten and other security frameworks. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in legacy systems, particularly those running outdated software versions that may contain undiscovered buffer overflow vulnerabilities.