CVE-2000-0503 in Internet Explorer
Summary
by MITRE
The IFRAME of the WebBrowser control in Internet Explorer 5.01 allows a remote attacker to violate the cross frame security policy via the NavigateComplete2 event.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2000-0503 represents a critical security flaw in Internet Explorer 5.01's WebBrowser control implementation that specifically targets the browser's cross-frame security mechanisms. This issue manifests through the IFRAME component of the WebBrowser control, which is designed to embed external content within web pages while maintaining security boundaries between different frames and domains. The vulnerability exploits a weakness in how the NavigateComplete2 event handler processes navigation completion within embedded frames, allowing malicious actors to bypass established security policies that normally prevent unauthorized cross-frame access.
The technical flaw occurs when the WebBrowser control's IFRAME component fails to properly enforce security restrictions during the NavigateComplete2 event processing phase. This event is triggered when a navigation operation within an IFRAME completes, but the control's implementation does not adequately validate or restrict access to resources that should be isolated between different security contexts. Attackers can leverage this weakness by crafting malicious web content that manipulates the NavigateComplete2 event to access or manipulate content from other frames that should be protected by cross-frame security policies. The vulnerability essentially allows a malicious frame to gain unauthorized access to the security context of another frame, potentially enabling information disclosure, cross-site scripting attacks, or other malicious activities that exploit the breakdown in security boundaries.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally undermines the browser's security model for frame isolation. When exploited, this vulnerability enables attackers to perform unauthorized actions such as reading data from different security domains, injecting malicious content into protected frames, or executing code in contexts where such access should be prohibited. The implications are particularly severe because the WebBrowser control is widely used in enterprise environments and applications that rely on Internet Explorer for embedded web content. This vulnerability could be exploited in phishing attacks, where attackers could craft pages that appear legitimate but actually access protected resources from other domains, or in more sophisticated attacks that leverage the cross-frame access to escalate privileges or extract sensitive information.
This vulnerability maps to CWE-200, which describes "Information Disclosure" and CWE-352, which covers "Cross-Site Request Forgery" in the context of cross-frame security violations. The attack patterns associated with this vulnerability align with techniques documented in the MITRE ATT&CK framework under the T1059 category for execution through web browsers, specifically targeting the browser's security model implementation. Organizations affected by this vulnerability should implement immediate mitigations including disabling IFRAME usage where possible, implementing strict content security policies, and ensuring that Internet Explorer 5.01 systems are updated to patched versions. The recommended approach includes network-level restrictions that prevent access to potentially malicious sites, browser configuration changes that disable problematic navigation event handlers, and comprehensive monitoring for suspicious cross-frame access patterns. Additionally, administrators should consider implementing web application firewalls and security scanning tools that can detect and prevent exploitation attempts targeting this specific vulnerability in legacy Internet Explorer installations.