CVE-2000-0266 in Internet Explorer
Summary
by MITRE
Internet Explorer 5.01 allows remote attackers to bypass the cross frame security policy via a malicious applet that interacts with the Java JSObject to modify the DOM properties to set the IFRAME to an arbitrary Javascript URL.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2000-0266 represents a critical security flaw in Internet Explorer 5.01 that undermines fundamental web security mechanisms. This weakness specifically targets the browser's cross-frame security policy, which is designed to prevent malicious code from accessing or modifying content across different frames or windows within a web page. The vulnerability exploits a legitimate but improperly secured interaction between Java applets and JavaScript within the browser environment, creating a pathway for attackers to circumvent these essential security boundaries.
The technical implementation of this vulnerability relies on the Java JSObject interface, which provides a bridge between Java applets and JavaScript environments within Internet Explorer. When a malicious applet executes, it can leverage the JSObject to directly manipulate Document Object Model properties, specifically targeting iframe elements. This allows the attacker to modify the iframe's source URL to point to arbitrary JavaScript content rather than the intended secure location. The flaw exists because the browser fails to properly validate or restrict these DOM modifications when initiated through the Java-to-JavaScript bridge, effectively enabling privilege escalation through the applet's elevated permissions.
The operational impact of this vulnerability is significant as it allows remote attackers to execute arbitrary JavaScript code within the context of a victim's browser session. Attackers can use this technique to perform cross-site scripting attacks, steal session cookies, manipulate web page content, or redirect users to malicious websites. The vulnerability is particularly dangerous because it operates at the browser level, bypassing traditional web application security controls and potentially allowing attackers to access sensitive information or perform unauthorized actions on behalf of users. This type of attack can be particularly effective in phishing campaigns where attackers can redirect users to malicious content while maintaining the appearance of legitimate web pages.
The vulnerability aligns with CWE-94, which describes improper control of generation of code, specifically in the context of code injection through insecure use of scripting languages. From an ATT&CK framework perspective, this corresponds to T1059.007 for JavaScript and T1211 for exploitation of web applications. Organizations should implement immediate mitigations including updating to newer versions of Internet Explorer, disabling Java applets in web browsers, and implementing strict content security policies. The recommended approach involves configuring browser security settings to restrict cross-frame scripting capabilities and ensuring that all users are running patched versions of the browser. Additionally, network-level protections such as web application firewalls and intrusion detection systems can help detect and prevent exploitation attempts targeting this specific vulnerability.