CVE-2025-54107 is a vulnerability classified under CWE-41 (Improper Resolution of Path Equivalence) affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw resides in the MapUrlToZone function, which Windows uses to determine the security zone of a URL (e.g., Internet, Local Intranet, Trusted Sites). Due to improper path equivalence resolution, an attacker can craft URLs that bypass zone-based security restrictions. This bypass can allow unauthorized access to resources or content that would normally be restricted by zone policies. The vulnerability is exploitable remotely over a network without requiring privileges but does require user interaction, such as clicking a malicious link. The CVSS v3.1 score is 4.3 (medium), reflecting low confidentiality impact, no integrity or availability impact, low attack complexity, no privileges required, but user interaction needed. No known exploits have been reported in the wild, and no patches have been published at the time of analysis. The vulnerability could be leveraged in phishing or social engineering attacks to circumvent security zones and access sensitive information or execute further attacks within a compromised environment. Since Windows 10 Version 1809 is an older release, many organizations may have already moved to newer versions, but legacy systems remain vulnerable.

For European organizations, the primary impact is a potential confidentiality breach where attackers bypass zone-based security controls to access restricted content or resources. This could facilitate further attacks such as credential theft, lateral movement, or data exfiltration if combined with other vulnerabilities or social engineering. The vulnerability does not affect system integrity or availability directly, limiting its destructive potential. However, organizations relying on Windows 10 Version 1809, particularly in sectors like government, finance, and critical infrastructure, may face increased risk due to legacy system usage. The need for user interaction means phishing campaigns could exploit this vulnerability to gain footholds. The absence of known exploits reduces immediate risk, but the lack of patches means the vulnerability remains open for future exploitation. Overall, the impact is moderate but significant in environments with outdated Windows versions and high-value targets.

1. Upgrade affected systems to a supported and patched version of Windows 10 or later, as Windows 10 Version 1809 is out of mainstream support and lacks official patches for this vulnerability. 2. Implement strict network filtering and URL filtering to block access to known malicious or untrusted URLs that could exploit this vulnerability. 3. Educate users to recognize and avoid clicking suspicious links, especially those received via email or messaging platforms. 4. Employ application whitelisting and endpoint protection solutions that can detect and block exploitation attempts involving URL manipulation. 5. Use group policy settings to restrict or disable automatic handling of URLs from untrusted zones where feasible. 6. Monitor network and endpoint logs for unusual access patterns or attempts to exploit URL zone bypass techniques. 7. Consider deploying web proxies or secure web gateways that enforce strict URL and content inspection to prevent malicious payload delivery. These measures collectively reduce the attack surface and limit the potential for exploitation despite the absence of an official patch.