CVE-2003-0447 in Internet Explorer
Summary
by MITRE
The Custom HTTP Errors capability in Internet Explorer 5.01, 5.5 and 6.0 allows remote attackers to execute script in the Local Zone via an argument to shdocvw.dll that causes a "javascript:" link to be generated.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 03/13/2025
The vulnerability described in CVE-2003-0447 represents a critical cross-site scripting flaw within Microsoft Internet Explorer versions 5.01, 5.5, and 6.0 that leverages the Custom HTTP Errors feature to execute arbitrary script code. This vulnerability specifically targets the shdocvw.dll component which handles the display of web content and error messages in the browser. The flaw occurs when Internet Explorer processes custom error pages that contain malicious arguments, enabling attackers to inject javascript code that gets executed within the Local Zone security context. This particular vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is a fundamental weakness in web applications that allows attackers to inject client-side scripts into web pages viewed by other users. The attack vector exploits the browser's handling of HTTP error responses and demonstrates how improper input validation can lead to privilege escalation within the browser's security model.
The technical exploitation of this vulnerability relies on the manipulation of the Custom HTTP Errors functionality that allows web servers to define custom error pages for various HTTP status codes. When Internet Explorer encounters an error condition and processes a custom error page, the shdocvw.dll component generates a "javascript:" link from the malicious argument provided by the attacker. This generated link executes within the Local Zone context, which has elevated privileges compared to the Internet Zone, allowing the malicious script to perform actions that would normally be restricted. The vulnerability specifically affects the way Internet Explorer handles the arguments passed to the shdocvw.dll library, where insufficient sanitization of input parameters leads to the injection of executable javascript code. This flaw demonstrates how browser components that handle error presentation can become attack vectors when they fail to properly validate or escape user-supplied data. The vulnerability is particularly dangerous because it operates within the Local Zone security boundary, which typically includes trusted intranet sites and local files that have more permissive security policies than external internet content.
The operational impact of CVE-2003-0447 extends beyond simple script execution to potentially enable full system compromise through a series of chained attacks. Attackers can leverage this vulnerability to steal user credentials, manipulate browser sessions, or redirect users to malicious websites that exploit additional vulnerabilities. The Local Zone context provides attackers with access to local resources and potentially sensitive data that is normally protected from internet-based attacks. This vulnerability can be particularly effective in corporate environments where users may browse both internal and external websites, as the Local Zone typically includes intranet resources that are trusted by default. The attack can be delivered through various means including malicious web pages, email attachments, or compromised websites that return custom error responses. Security researchers have noted that this vulnerability often serves as a stepping stone for more sophisticated attacks, as the initial script execution can be used to download and execute additional malware payloads. The impact is further amplified by the widespread adoption of Internet Explorer 5.x and 6.0 versions at the time of the vulnerability disclosure, making it a significant threat vector for organizations with legacy browser deployments.
Mitigation strategies for CVE-2003-0447 require both immediate and long-term approaches to address the underlying security flaw. Microsoft released security patches that updated the shdocvw.dll component to properly sanitize input arguments and prevent the generation of malicious javascript links from error responses. Organizations should implement immediate browser updates and security patches to protect against exploitation of this vulnerability. The recommended mitigation includes upgrading to newer versions of Internet Explorer that have fixed this vulnerability, as well as implementing proper input validation at the web server level to prevent malicious arguments from being passed to browser components. Network-based security controls such as web application firewalls and content filtering systems can provide additional protection by monitoring for suspicious javascript patterns in HTTP error responses. Users should be educated about the risks of visiting untrusted websites and the importance of keeping their browsers updated. Security administrators should also consider implementing browser security policies that restrict the execution of scripts in the Local Zone and disable unnecessary features like Custom HTTP Errors. This vulnerability highlights the importance of proper input validation and the need for defense-in-depth security measures, as it demonstrates how a single flaw in a core browser component can enable widespread exploitation across multiple attack vectors. The remediation process should also include monitoring for exploitation attempts and implementing appropriate incident response procedures to address potential compromise of affected systems.