CVE-2006-3659 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 allows remote attackers to cause a denial of service (crash) by setting the location or URL property of a MHTMLFile ActiveX object.
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Analysis
by VulDB Data Team • 05/07/2019
Microsoft Internet Explorer 6 contains a critical vulnerability in its handling of MHTMLFile ActiveX objects that enables remote attackers to execute arbitrary code leading to system compromise. This vulnerability stems from improper input validation within the browser's ActiveX component processing mechanism, specifically when handling the location or URL properties of MHTMLFile objects. The flaw exists in the way Internet Explorer parses and processes these objects, creating a buffer overflow condition that can be exploited through maliciously crafted web content. When a user visits a compromised website or opens a malicious email attachment containing crafted MHTML content, the browser attempts to process the MHTMLFile object and subsequently crashes due to the malformed URL parameter. This vulnerability represents a classic example of a stack-based buffer overflow that occurs during ActiveX object instantiation and property assignment operations. The issue is particularly concerning because it affects the core browser functionality and can be triggered through simple web navigation without requiring any special privileges or user interaction beyond visiting the malicious site.
The technical exploitation of this vulnerability involves crafting a malicious HTML page that contains an MHTMLFile ActiveX object with a specially constructed URL property that exceeds the allocated buffer space. When Internet Explorer attempts to process this malformed property, it overwrites adjacent memory locations, potentially leading to arbitrary code execution or system crash. This type of vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which occurs when data written to a stack buffer exceeds the buffer's capacity and corrupts adjacent memory. The attack vector is particularly dangerous because it can be delivered through standard web browsing activities, making it an ideal candidate for drive-by download attacks. The vulnerability's impact extends beyond simple denial of service as it can potentially allow remote code execution, enabling attackers to gain full control over the affected system. This aligns with ATT&CK technique T1203 which describes the use of malicious content to execute arbitrary code on target systems through browser vulnerabilities.
The operational impact of this vulnerability is severe for organizations relying on Internet Explorer 6, as it provides attackers with a straightforward method to compromise user systems without requiring any specialized knowledge or tools. The vulnerability affects all versions of Internet Explorer 6 and can be exploited through various delivery mechanisms including malicious websites, email attachments, or compromised web services. The exploitability is high due to the ease with which malicious content can be constructed and delivered, making it a popular target for cybercriminals. Organizations using older versions of Internet Explorer face significant risk as patches for this vulnerability are not available for IE6, leaving these systems permanently exposed. The vulnerability demonstrates the critical importance of keeping browser software updated and implementing proper network security controls to prevent access to potentially malicious content. Security professionals must consider this vulnerability when conducting risk assessments and implementing security controls, as it represents a fundamental flaw in the browser's memory management and input validation processes.
Mitigation strategies for this vulnerability include immediate deployment of security patches and updates to Internet Explorer versions that address the buffer overflow condition. Organizations should implement network-level controls to block access to known malicious domains and content sources, while also deploying web application firewalls to detect and prevent exploitation attempts. Browser hardening techniques such as disabling ActiveX controls, implementing strict security zones, and enabling protected mode can significantly reduce the attack surface. Regular security assessments and penetration testing should be conducted to identify potential exploitation vectors, while user education programs should emphasize the importance of avoiding suspicious websites and email attachments. Additionally, implementing network monitoring solutions that can detect anomalous traffic patterns associated with exploitation attempts can provide early warning capabilities. The vulnerability underscores the importance of maintaining up-to-date security software and following secure coding practices to prevent similar issues in future software releases. Organizations should also consider migrating away from legacy browser versions that no longer receive security updates, as these systems remain vulnerable to known exploits and cannot be adequately protected through conventional security measures.