CVE-2000-0400 in Active Movie Control
Summary
by MITRE
The Microsoft Active Movie ActiveX Control in Internet Explorer 5 does not restrict which file types can be downloaded, which allows an attacker to download any type of file to a user's system by encoding it within an email message or news post.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2000-0400 represents a critical security flaw in Microsoft Internet Explorer 5's handling of ActiveX controls, specifically the Active Movie ActiveX control. This issue stems from insufficient input validation and file type restriction mechanisms within the browser's ActiveX integration framework. The vulnerability allows malicious actors to exploit the control's design to download arbitrary file types to users' systems without proper authorization or user consent, creating a significant attack surface for various malicious activities.
The technical flaw manifests in the Active Movie ActiveX control's failure to implement proper file type validation when processing download requests. When users encounter specially crafted email messages or news posts containing malicious ActiveX code, the control executes without verifying whether the requested file type is appropriate or safe for execution. This lack of restriction enables attackers to download potentially harmful files such as executable programs, script files, or other malicious payloads directly to the victim's system. The vulnerability is particularly dangerous because it leverages the trust relationship between the browser and ActiveX controls, allowing attackers to bypass normal security restrictions that would otherwise prevent unauthorized file downloads.
The operational impact of this vulnerability extends beyond simple file downloads, creating multiple attack vectors for cybercriminals. Attackers can use this flaw to deploy malware, trojans, or other malicious software without requiring users to explicitly interact with suspicious content. The vulnerability is particularly effective in phishing campaigns and social engineering attacks where users might be tricked into opening email messages or browsing news posts that contain the malicious ActiveX code. Additionally, the flaw can be exploited in conjunction with other vulnerabilities to create more sophisticated attack chains, potentially leading to complete system compromise. The vulnerability affects all versions of Internet Explorer 5 that include the Active Movie ActiveX control, making it a widespread concern across numerous systems.
This vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic example of how inadequate security controls in browser components can create significant risks. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1193 (Spearphishing Attachment) and T1059 (Command and Scripting Interpreter) where attackers can leverage the control to execute malicious code. The flaw also demonstrates the broader category of T1203 (Exploitation for Client Execution) where attackers exploit browser vulnerabilities to gain code execution capabilities on target systems. Mitigation strategies should include disabling ActiveX controls, implementing strict content filtering, and applying security updates from Microsoft. Organizations should also consider network-level restrictions to prevent automatic downloads of potentially malicious files and implement user education programs to reduce the risk of successful exploitation through social engineering techniques.