CVE-2003-0838 in Internet Explorer
Summary
by MITRE
Internet Explorer allows remote attackers to bypass zone restrictions to inject and execute arbitrary programs by creating a popup window and inserting ActiveX object code with a "data" tag pointing to the malicious code, which Internet Explorer treats as HTML or Javascript, but later executes as an HTA application, a different vulnerability than CVE-2003-0532, and as exploited using the QHosts Trojan horse (aka Trojan.Qhosts, QHosts-1, VBS.QHOSTS, or aolfix.exe).
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Analysis
by VulDB Data Team • 03/17/2025
This vulnerability represents a sophisticated cross-domain execution flaw in Microsoft Internet Explorer that exploits the browser's handling of ActiveX controls and zone security mechanisms. The vulnerability specifically targets the way Internet Explorer processes popup windows and ActiveX objects, creating a path for remote code execution that bypasses standard security zone restrictions. Attackers can leverage this weakness by crafting malicious HTML content that appears to be standard web content but is actually designed to execute with elevated privileges through the HTA application execution path.
The technical mechanism involves the exploitation of Internet Explorer's data URI handling capabilities combined with ActiveX control injection. When a malicious popup window is created, the attacker can embed an ActiveX object with a data tag that points to malicious code. This code is initially interpreted by the browser as HTML or JavaScript content but is subsequently executed as an HTA (HTML Application) application, which operates with different security permissions than standard web content. The vulnerability demonstrates a fundamental flaw in the browser's content type detection and execution model, where the same data can be interpreted differently based on context and execution path.
The operational impact of this vulnerability is significant as it allows attackers to execute arbitrary code on vulnerable systems without requiring user interaction beyond visiting a malicious website. The exploitation technique specifically leverages the QHosts Trojan horse, which is a well-documented malware family that has been used in various phishing and malware campaigns. This vulnerability affects systems running vulnerable versions of Internet Explorer, particularly those that do not have proper security patches applied, and can be exploited across different operating system versions that include the affected browser components.
The attack vector demonstrates characteristics consistent with the CWE-749 weakness category, which addresses "Expose of Functionality to Unintended Actors" and specifically involves the exposure of dangerous functionality through improper access control. This vulnerability also aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript' and T1059.005 for 'Command and Scripting Interpreter: Visual Basic' as it leverages scripting languages and ActiveX controls to execute malicious code. The exploitation requires a combination of browser vulnerabilities and social engineering to achieve successful compromise, making it particularly dangerous in targeted attack scenarios.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Internet Explorer versions, implementing proper zone security settings, and disabling ActiveX controls where possible. Organizations should also deploy network-based protections such as web application firewalls and content filtering solutions to detect and block malicious data URI requests. Browser hardening measures including disabling popup windows, restricting ActiveX control installation, and implementing strict security policies for zone-based access control can significantly reduce the attack surface. Additionally, user education and awareness programs should emphasize the dangers of visiting untrusted websites and the importance of keeping browser software updated with the latest security patches.