CVE-2006-3357 in Internet Explorer
Summary
by MITRE
Heap-based buffer overflow in HTML Help ActiveX control (hhctrl.ocx) in Microsoft Internet Explorer 6.0 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code by repeatedly setting the Image field of an Internet.HHCtrl.1 object to certain values, possibly related to improper escaping and long strings.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/21/2025
The vulnerability described in CVE-2006-3357 represents a critical heap-based buffer overflow affecting the HTML Help ActiveX control hhctrl.ocx in Microsoft Internet Explorer 6.0. This flaw resides within the Internet.HHCtrl.1 object implementation where the Image field property handling fails to properly validate input length and escaping mechanisms. The vulnerability manifests when attackers repeatedly set the Image field to specific values that trigger memory corruption through improper string handling and buffer management. The heap-based nature of this overflow indicates that the vulnerable code allocates memory on the heap and subsequently writes beyond allocated boundaries, creating potential for arbitrary code execution or application instability.
The technical implementation of this vulnerability leverages the ActiveX control's improper handling of the Image field parameter which likely lacks proper bounds checking and input sanitization. When malicious values are repeatedly assigned to this field, the control's internal buffer management routines fail to account for the extended string lengths and improper escaping sequences, leading to memory corruption in the heap allocation regions. This specific flaw falls under CWE-121, heap-based buffer overflow, and aligns with ATT&CK technique T1059.007 for executing arbitrary code through ActiveX controls. The vulnerability's exploitation requires the target system to have Internet Explorer 6.0 installed with the vulnerable hhctrl.ocx control, making it particularly dangerous in legacy environments where users may not have updated their browsers.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it a severe security risk for affected systems. When exploited successfully, the buffer overflow can cause Internet Explorer to crash or more dangerously allow attackers to execute malicious code with the privileges of the user running the browser. The repeated setting of the Image field parameter creates a pattern that can be automated, enabling attackers to craft payloads that trigger the overflow consistently. This vulnerability particularly affects enterprise environments where Internet Explorer 6.0 may still be in use due to legacy application dependencies or lack of security updates, creating persistent attack vectors that can be leveraged by threat actors to compromise systems. Organizations with outdated browser versions remain vulnerable to this type of attack vector that exploits fundamental memory management flaws in ActiveX controls.
Mitigation strategies for CVE-2006-3357 require immediate action to update Internet Explorer to supported versions or implement security controls that prevent ActiveX control execution. Microsoft released security updates addressing this vulnerability through their regular patching cycle, but the most effective defense involves comprehensive browser modernization and deprecation of Internet Explorer 6.0 in favor of supported browser versions. Organizations should implement application whitelisting policies to restrict ActiveX control execution and deploy security solutions that monitor for suspicious ActiveX behavior patterns. The vulnerability demonstrates the importance of proper input validation and memory management practices in software development, aligning with security best practices outlined in the OWASP Top Ten and NIST cybersecurity frameworks. Regular security assessments and vulnerability scanning should specifically target ActiveX controls and legacy browser components to identify and remediate similar memory corruption vulnerabilities before they can be exploited in the wild.