CVE-2006-3639 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 5.01 and 6 does not properly identify the originating domain zone when handling redirects, which allows remote attackers to read cross-domain web pages and possibly execute code via unspecified vectors involving a crafted web page, aka "Source Element Cross-Domain Vulnerability."
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Analysis
by VulDB Data Team • 01/05/2025
The vulnerability identified as CVE-2006-3639 represents a critical cross-domain security flaw in Microsoft Internet Explorer versions 5.01 and 6. This issue stems from the browser's improper handling of domain zone identification during redirect operations, creating a fundamental breach in the security model that separates different trust zones. The flaw specifically affects how Internet Explorer determines the originating domain zone when processing web redirects, allowing malicious actors to exploit this weakness to access content from different domains that should normally be restricted. This vulnerability operates at the core of browser security architecture, undermining the essential principle that web pages from different domains should be isolated from each other to prevent unauthorized data access and potential code execution. The security implications extend beyond simple data theft, as the vulnerability could enable attackers to craft malicious web pages that exploit the trust relationship between different domain zones.
The technical mechanism behind this vulnerability involves the browser's failure to properly validate or identify the source domain zone when handling redirect responses from web servers. When Internet Explorer processes a redirect, it should verify that the target domain belongs to the same security zone as the original request, but this validation process is flawed in the affected versions. Attackers can exploit this by creating a malicious web page that triggers a redirect to a different domain while maintaining the illusion of a trusted source. This allows the browser to execute code in a context that should normally be restricted, potentially enabling cross-domain data reading and execution capabilities that violate the fundamental security boundaries of the browser's zone-based security model. The vulnerability specifically impacts the source element handling within the browser's security architecture, where the origin zone determination fails to properly validate cross-domain transitions. This issue is particularly dangerous because it operates below the application layer, affecting the browser's core security mechanisms rather than being a simple application-level flaw.
The operational impact of CVE-2006-3639 is severe and far-reaching, as it effectively allows remote attackers to bypass critical security boundaries that protect users from malicious cross-domain attacks. Attackers can construct sophisticated web pages that leverage this vulnerability to access sensitive information from different domains, potentially including corporate networks, financial systems, or personal data repositories that should be protected by the browser's security model. The unspecified vectors mentioned in the vulnerability description suggest that multiple attack scenarios are possible, including the ability to execute arbitrary code on vulnerable systems. This vulnerability represents a classic example of a privilege escalation issue within the browser's security architecture, where an attacker can gain access to resources that should be restricted based on domain zone membership. The impact extends to enterprise environments where users may access both internal and external resources, as the vulnerability could allow attackers to move laterally between different trust domains within a network.
Mitigation strategies for this vulnerability require immediate action from system administrators and security teams to address the fundamental browser security flaw. The most effective approach involves applying the security patches released by Microsoft as part of their regular security updates, which correct the domain zone identification logic during redirect operations. Organizations should also implement additional security measures including browser hardening configurations, network-based restrictions, and user education about the risks of visiting untrusted websites. The vulnerability aligns with CWE-200, which addresses improper information exposure, and can be mapped to ATT&CK techniques involving privilege escalation and credential access through browser exploitation. Security professionals should consider implementing web application firewalls and network monitoring solutions to detect and block malicious redirects that attempt to exploit this vulnerability. Additionally, organizations should conduct comprehensive security assessments to identify any systems running the vulnerable Internet Explorer versions and ensure complete remediation through proper patch management processes. The vulnerability demonstrates the critical importance of maintaining up-to-date browser security implementations and highlights the need for continuous monitoring of security advisories from vendors and security organizations to protect against similar issues in the future.