CVE-2006-3898 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 on Windows XP SP2 allows remote attackers to cause a denial of service (application crash) by calling the Click method of the Internet.HHCtrl.1 ActiveX object before initializing the URL, which triggers a null dereference.
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability described in CVE-2006-3898 represents a classic null pointer dereference flaw within Microsoft Internet Explorer 6.0 running on Windows XP Service Pack 2 systems. This issue specifically affects the Internet.HHCtrl.1 ActiveX object, which is part of the Microsoft HTML Help system and is commonly used for displaying help documentation within web applications. The vulnerability arises from improper initialization handling within the Click method of this ActiveX control, creating a scenario where an attacker can manipulate the object state to trigger a critical application error.
The technical execution of this vulnerability involves exploiting the lack of proper input validation and state management within the ActiveX control. When an attacker crafts a malicious web page that invokes the Click method of the Internet.HHCtrl.1 object without first properly initializing the URL parameter, the application attempts to dereference a null pointer, leading to an unhandled exception. This null dereference condition causes Internet Explorer to crash and terminate the application process, resulting in a denial of service condition that prevents legitimate users from accessing the affected system. The vulnerability is particularly concerning because it can be triggered through web-based attacks without requiring any user interaction beyond visiting a malicious website, making it a significant remote exploitation vector.
From an operational impact perspective, this vulnerability exposes organizations running legacy Internet Explorer 6.0 systems to potential disruption of critical business operations. The denial of service condition affects not just individual user sessions but can potentially impact entire network operations if multiple users are accessing the same vulnerable systems. The vulnerability aligns with CWE-476 which specifically addresses null pointer dereference conditions, and it demonstrates how ActiveX controls can become attack surfaces when proper state management and input validation are absent. Organizations with outdated systems running IE6 are particularly vulnerable as these systems lack modern security mitigations and are no longer supported with security updates.
The attack pattern for this vulnerability follows standard remote code execution methodologies documented in the MITRE ATT&CK framework, specifically mapping to techniques involving application layer attacks through web browsers. The exploitation requires minimal privileges and can be delivered through various web-based attack vectors including malicious websites, email attachments, or compromised web servers. Given that Internet Explorer 6.0 was widely deployed in enterprise environments during this timeframe, the potential impact was significant across multiple organizations. The vulnerability underscores the importance of proper software lifecycle management and the risks associated with running unsupported browser versions that no longer receive security patches. Organizations should implement immediate mitigations including browser updates, network segmentation, and the deployment of web application firewalls to prevent exploitation of this and similar vulnerabilities. The incident serves as a critical reminder of how seemingly minor programming flaws in ActiveX controls can result in substantial security implications when exploited by remote attackers.