CVE-2003-1328 in Internet Explorer
Summary
by MITRE
The showHelp() function in Microsoft Internet Explorer 5.01, 5.5, and 6.0 supports certain types of pluggable protocols that allow remote attackers to bypass the cross-domain security model and execute arbitrary code, aka "Improper Cross Domain Security Validation with ShowHelp functionality."
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Analysis
by VulDB Data Team • 03/15/2025
The vulnerability described in CVE-2003-1328 represents a critical cross-domain security flaw within Microsoft Internet Explorer versions 5.01, 5.5, and 6.0. This issue specifically affects the showHelp() function which is designed to provide help functionality within the browser environment. The vulnerability stems from improper validation of pluggable protocols that are supported by this function, creating a pathway for malicious actors to circumvent the browser's fundamental security boundaries that normally prevent cross-domain script execution.
The technical implementation of this vulnerability allows remote attackers to exploit the showHelp() function's handling of certain protocol handlers, particularly those that can be manipulated to execute code outside the intended security context. When Internet Explorer processes help requests through this function, it fails to properly validate the domain boundaries of the protocols being invoked, enabling attackers to craft malicious web pages that can execute arbitrary code with the privileges of the user's browser session. This flaw directly violates the core security principle of same-origin policy enforcement that browsers implement to prevent unauthorized cross-domain operations.
The operational impact of this vulnerability is severe as it provides attackers with a means to bypass the browser's security model entirely, potentially allowing them to execute malicious code on victim machines without requiring any user interaction beyond visiting a compromised website. Attackers can leverage this vulnerability to perform actions such as downloading and executing malware, accessing local files, modifying browser settings, or even gaining access to sensitive user data. The vulnerability affects a wide range of Internet Explorer versions, making it particularly dangerous as many users were still operating on older browser versions at the time of discovery.
This vulnerability maps directly to CWE-94, which describes "Improper Control of Generation of Code" and aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter. The flaw demonstrates how protocol handler implementations can create security gaps that allow attackers to escalate privileges beyond normal browser security boundaries. Organizations affected by this vulnerability should immediately implement patches from Microsoft, disable the problematic showHelp() functionality, and consider implementing network-level protections such as web application firewalls to prevent exploitation attempts. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping browsers updated to prevent exploitation of such fundamental security flaws.