CVE-1999-0668 is a vulnerability in Microsoft Internet Explorer versions 4.0 and 5.0 involving the scriptlet.typelib ActiveX control. This control is incorrectly marked as "safe for scripting," which means that web pages can instantiate and interact with it via scripting languages such as JavaScript without user prompts or restrictions. The vulnerability allows a remote attacker to execute arbitrary commands on the victim's system by leveraging this control. The exploit, demonstrated by the Bubbleboy attack, enables code execution within the security context of the user running Internet Explorer. This can lead to unauthorized actions such as file manipulation, system configuration changes, or launching further malware. The vulnerability is network exploitable without authentication but requires the victim to visit a malicious or compromised web page. The CVSS score of 5.1 (medium severity) reflects the moderate ease of exploitation due to the need for user interaction (visiting a malicious site) and the presence of some attack complexity. A patch addressing this vulnerability was released by Microsoft in 1999 (MS99-032), which removes the "safe for scripting" designation from the control or disables it entirely. Despite its age, this vulnerability highlights the risks of unsafe ActiveX controls and the importance of secure component marking and sandboxing in browsers.

For European organizations, the impact of this vulnerability historically would have been significant, especially for those relying on legacy systems or outdated versions of Internet Explorer. Successful exploitation could lead to unauthorized code execution, potentially compromising confidentiality, integrity, and availability of affected systems. This could result in data breaches, unauthorized access to sensitive information, or disruption of business operations. Although modern browsers and updated systems have mitigated this risk, organizations still running legacy environments or using Internet Explorer in compatibility modes may remain vulnerable. Additionally, the vulnerability could be leveraged as part of multi-stage attacks targeting European enterprises, especially those in sectors with legacy infrastructure such as government, manufacturing, or critical infrastructure. The risk is compounded by the fact that exploitation requires only that a user visits a malicious web page, making phishing or drive-by download attacks feasible vectors.

European organizations should ensure that all systems have been updated to versions of Internet Explorer that include the MS99-032 patch or later security updates. Specifically, removing or disabling the scriptlet.typelib ActiveX control or ensuring it is not marked as "safe for scripting" is critical. Organizations should phase out use of Internet Explorer 4.0 and 5.0 entirely, migrating to modern browsers with improved security models that do not rely on ActiveX controls. Network defenses such as web filtering and URL reputation services can help block access to known malicious sites that might exploit this vulnerability. User education to avoid clicking on suspicious links or visiting untrusted websites is also important. For legacy systems that cannot be upgraded immediately, running Internet Explorer in restricted or enhanced security modes, or using application whitelisting and endpoint protection solutions, can reduce risk. Regular vulnerability scanning and asset inventory to identify any remaining vulnerable systems will help prioritize remediation efforts.