CVE-2000-0028 is a security vulnerability affecting Microsoft Internet Explorer versions 3.0 through 5.1, including 5.0 and 5.01. The flaw allows remote attackers to bypass the browser's cross-frame security policy, which is designed to prevent a webpage from accessing or manipulating content in another frame from a different origin. Specifically, the vulnerability exploits the external.NavigateAndFind function, enabling an attacker to read files that should be protected by the same-origin policy. This bypass can lead to unauthorized disclosure of sensitive information stored or accessible via the browser. The vulnerability was disclosed in late 1999 and has a CVSS base score of 2.6, indicating a low severity level. The attack vector is network-based, requires no authentication, but has high attack complexity, and impacts confidentiality only without affecting integrity or availability. No patches or fixes were made available, likely due to the age of the affected software and its obsolescence. There are no known exploits in the wild documented for this vulnerability.

For European organizations, the impact of CVE-2000-0028 is minimal in the current context due to the obsolescence of the affected Internet Explorer versions (3.0 to 5.1). Modern browsers have long since replaced these versions, and most organizations have migrated to updated software with improved security controls. However, in legacy environments where these old IE versions might still be in use—such as in industrial control systems, legacy intranet applications, or isolated networks—there remains a risk of sensitive data exposure through cross-frame scripting attacks. The vulnerability could allow attackers to read local or network files accessible via the browser, potentially leaking confidential information. Given the low CVSS score and absence of known exploits, the threat is not critical but should be considered in legacy system risk assessments. European organizations with strict data protection regulations (e.g., GDPR) should be cautious about any residual use of vulnerable browsers that could lead to data leaks.

Since no official patches are available for this vulnerability, the primary mitigation is to discontinue use of affected Internet Explorer versions entirely. Organizations should upgrade to modern, supported browsers that enforce robust same-origin policies and have mitigations against cross-frame scripting attacks. For legacy systems that cannot be upgraded immediately, network segmentation and strict access controls should be implemented to isolate vulnerable machines from untrusted networks. Additionally, disabling or restricting the use of the external.NavigateAndFind function via browser configuration or group policy (if possible) can reduce exposure. Regular security audits should identify any remaining legacy browser usage, and user training should emphasize the risks of outdated software. Employing web application firewalls (WAFs) and endpoint security solutions that monitor for suspicious browser behavior may also help detect exploitation attempts.