CVE-2006-0057 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 5.01, 5.5, and 6 allows remote attackers to bypass the Kill bit settings for dangerous ActiveX controls via unknown vectors involving crafted HTML, which can expose the browser to attacks that would otherwise be prevented by the Kill bit setting. NOTE: CERT/CC claims that MS05-054 fixes this issue, but it is not described in MS05-054.
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Analysis
by VulDB Data Team • 11/23/2024
The vulnerability described in CVE-2006-0057 represents a critical security flaw in Microsoft Internet Explorer versions 5.01, 5.5, and 6 that undermines the browser's fundamental security controls. This issue specifically targets the Kill bit mechanism, which serves as a critical defense mechanism designed to prevent the execution of potentially malicious ActiveX controls that have been identified as dangerous by Microsoft. The Kill bit functionality operates by maintaining a registry-based blacklist of ActiveX controls that should be disabled when encountered in web content, thereby preventing exploitation of known vulnerabilities in these components. When an ActiveX control is marked with a Kill bit, the browser should automatically disable its execution regardless of user permissions or other factors, creating a robust security barrier against known threats.
The technical flaw exploited in this vulnerability occurs when attackers craft specially designed HTML content that can bypass the Kill bit protections through mechanisms that remain unspecified in the original CVE description. This allows malicious actors to circumvent the intended security restrictions and execute dangerous ActiveX controls that would normally be blocked by the Kill bit mechanism. The vulnerability operates at the browser's security parsing layer, where crafted HTML elements can manipulate how the browser interprets and applies security policies for ActiveX control execution. This represents a fundamental failure in the browser's security model where the Kill bit protection mechanism can be bypassed through carefully constructed web content that exploits implementation gaps in the security enforcement logic. The vulnerability affects all versions of Internet Explorer that support ActiveX controls, creating a wide attack surface across multiple generations of the browser.
The operational impact of this vulnerability is severe and far-reaching, as it allows remote attackers to execute arbitrary code on vulnerable systems with the privileges of the user running the browser. When an attacker successfully exploits this vulnerability, they can effectively bypass the security controls that Microsoft had implemented to protect users from known dangerous ActiveX controls, potentially leading to complete system compromise. The attack vector involves delivering malicious HTML content to a victim's browser, which then executes the crafted elements to bypass the Kill bit protection and load the dangerous ActiveX control. This creates a significant risk for enterprise environments where users may encounter malicious web content through various attack vectors including email attachments, compromised websites, or social engineering campaigns. The vulnerability undermines the trust model that Microsoft had established through its Kill bit system, making it possible for attackers to exploit known security holes in ActiveX controls that should have been permanently disabled.
Organizations affected by this vulnerability should immediately implement mitigations through Microsoft's security updates, particularly noting that CERT/CC indicates MS05-054 addresses this issue despite the lack of explicit documentation in the security bulletin. The recommended approach involves applying the appropriate security patches that correct the implementation flaw in the Kill bit enforcement mechanism. Additionally, system administrators should consider implementing browser hardening measures including disabling ActiveX controls entirely where possible, implementing strict content filtering policies, and deploying intrusion detection systems to monitor for exploitation attempts. The vulnerability demonstrates the importance of comprehensive security testing and the need for layered defenses, as a single flaw in the Kill bit implementation can completely undermine the security posture of systems relying on this protection mechanism. This vulnerability aligns with CWE-119, which describes weaknesses in memory handling that can lead to privilege escalation, and represents a significant concern for organizations that continue to support legacy Internet Explorer versions where such patches may not be available. The attack pattern associated with this vulnerability is consistent with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for privilege escalation, and highlights the critical need for maintaining up-to-date security patches across all supported browser versions.