CVE-2004-0201 in Windows
Summary
by MITRE
Heap-based buffer overflow in the HtmlHelp program (hh.exe) in HTML Help for Microsoft Windows 98, Me, NT 4.0, 2000, XP, and Server 2003 allows remote attackers to execute arbitrary commands via a .CHM file with a large length field, a different vulnerability than CVE-2003-1041.
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Analysis
by VulDB Data Team • 01/02/2025
The vulnerability described in CVE-2004-0201 represents a critical heap-based buffer overflow flaw within the HtmlHelp program component hh.exe that shipped with various Microsoft Windows operating systems including Windows 98 Me NT 4.0 2000 XP and Server 2003. This issue specifically affects the HTML Help subsystem which is responsible for displaying help files and documentation within the Windows environment. The vulnerability manifests when the HtmlHelp program processes .CHM files that contain malformed data with excessively large length fields that exceed the allocated buffer space in memory. This particular flaw operates at the heap memory level where dynamic memory allocation occurs, making it particularly dangerous as it can lead to arbitrary code execution when exploited by remote attackers. The vulnerability is distinct from CVE-2003-1041 which addressed a different class of issues within the same subsystem, indicating that Microsoft had already identified and addressed some buffer overflow concerns but failed to resolve this specific heap-based variant.
The technical implementation of this vulnerability involves the improper handling of data structures within the .CHM file format when the HtmlHelp program attempts to parse and process help content. When a specially crafted .CHM file contains a length field that exceeds the expected buffer boundaries the program fails to perform adequate bounds checking before copying data into heap-allocated memory regions. This allows attackers to overwrite adjacent memory locations with malicious data, potentially corrupting program execution flow and enabling code injection attacks. The heap-based nature of the overflow means that the attacker can manipulate memory pointers and function return addresses within the program's execution context, leading to complete system compromise when successful exploitation occurs. The vulnerability's remote exploitability stems from the fact that .CHM files can be delivered through various network channels including email attachments web downloads and network shares, making it particularly dangerous for widespread exploitation.
The operational impact of CVE-2004-0201 extends beyond simple denial of service scenarios to encompass full system compromise capabilities that align with ATT&CK technique T1059 for command and script interpreter execution. This vulnerability enables attackers to execute arbitrary code with the privileges of the user running the HtmlHelp program, which typically runs with the same privileges as the user who initiated the help file viewing operation. The attack surface is extensive given that .CHM files are commonly used throughout Windows systems for documentation and help purposes, making legitimate file delivery channels vulnerable to exploitation. Organizations using affected Windows versions face significant risk as the vulnerability can be exploited through social engineering tactics that trick users into opening malicious help files, potentially leading to complete system takeover and persistent access. The vulnerability's presence in multiple Windows versions including legacy operating systems means that many organizations may still be exposed despite the age of the flaw.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security posture improvements. The primary and most effective mitigation involves applying Microsoft security patches that address the heap overflow in the HtmlHelp program component, which were released as part of the regular Windows security update cycle. Organizations should implement strict file type controls and user education programs to prevent users from opening untrusted .CHM files from unknown sources. Network-level controls including firewall rules and web content filtering can help prevent the delivery of malicious .CHM files through email and web-based attack vectors. System hardening measures such as disabling unnecessary help file processing capabilities and implementing least privilege access controls can reduce the potential impact of successful exploitation. Additionally, organizations should consider implementing application whitelisting policies that restrict the execution of potentially vulnerable programs and monitor for unusual file access patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management practices in software development, aligning with CWE-121 which addresses heap-based buffer overflow conditions and the broader category of memory safety issues that continue to plague software systems.