CVE-2005-0110 in Internet Explorer
Summary
by MITRE
Internet Explorer 6 on Windows XP SP2 allows remote attackers to bypass the file download warning dialog and possibly trick an unknowledgeable user into executing arbitrary code via a web page with a body element containing an onclick tag, as demonstrated using the createElement function.
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Analysis
by VulDB Data Team • 07/01/2021
This vulnerability represents a critical browser security flaw in Internet Explorer 6 running on Windows XP Service Pack 2 that undermines fundamental user protection mechanisms. The issue stems from a design weakness in how IE handles certain HTML elements and JavaScript execution contexts, specifically when processing the body element with onclick attributes within crafted web pages. The vulnerability exploits a bypass mechanism that allows malicious code to circumvent the built-in file download warnings that are intended to alert users before executing potentially harmful content. This represents a direct violation of security model principles where user consent and awareness are paramount for protecting against malicious downloads.
The technical implementation of this exploit relies on the interaction between the createElement JavaScript function and the onclick event handler within the body element of HTML documents. When a malicious web page constructs an element using createElement and immediately attaches an onclick handler, the browser's security model fails to properly validate the context in which this execution occurs. This creates an opportunity for attackers to inject malicious code that can execute without proper user notification or consent. The vulnerability demonstrates a classic case of insufficient input validation and improper privilege separation between different execution contexts within the browser environment. This flaw aligns with CWE-693, which addresses protection mechanism failures, and specifically relates to CWE-20, input validation issues, where the browser fails to properly validate the security context of dynamically generated elements.
The operational impact of this vulnerability extends beyond simple code execution to encompass a complete breakdown of user protection mechanisms designed to prevent accidental malware installation. Users who encounter such malicious web pages may unknowingly download and execute harmful software without receiving the expected warning dialog that would typically alert them to the potential danger. This creates a significant risk for enterprise environments where users may not be security-aware and could inadvertently compromise systems through seemingly benign web browsing activities. The vulnerability particularly affects organizations running legacy systems where Windows XP SP2 with IE6 remains in use, creating persistent exposure windows for attackers targeting these specific configurations. According to ATT&CK framework, this vulnerability maps to T1203 - Exploitation for Client Execution and T1059 - Command and Scripting Interpreter, as it enables attackers to execute malicious code through browser-based vectors.
Mitigation strategies for this vulnerability require immediate remediation through system updates and security patches provided by Microsoft, as well as organizational policies that restrict browser usage to supported versions. Organizations should implement network-level controls to block access to known malicious domains and consider deploying web application firewalls that can detect and prevent the exploitation patterns associated with this vulnerability. Browser security hardening measures, including disabling JavaScript in untrusted environments and implementing strict content security policies, provide additional protective layers. Regular security awareness training for users helps reduce the risk of successful exploitation by educating them about the importance of heeding security warnings and recognizing potentially malicious web content. The vulnerability underscores the critical importance of maintaining up-to-date security software and the dangers of running unsupported operating systems and browsers in enterprise environments where security controls are paramount.