CVE-2025-54107 is a medium-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw stems from improper resolution of path equivalence within the Windows MapUrlToZone function. This function is responsible for mapping URLs to security zones, which is a critical security feature used to enforce zone-based restrictions on content and scripts. Due to this improper path equivalence resolution, an unauthorized attacker can bypass security controls over a network. Specifically, the vulnerability allows an attacker to craft a malicious URL or network resource path that is incorrectly resolved by the system, thereby circumventing security zone policies designed to restrict potentially harmful content. The vulnerability does not require any privileges (PR:N), but does require user interaction (UI:R), such as convincing a user to access a malicious link or resource. The attack vector is network-based (AV:N), meaning exploitation can occur remotely without local access. The impact is limited to confidentiality (C:L), with no direct impact on integrity or availability. No known exploits are currently reported in the wild, and no official patches or mitigation guidance have been published at this time. The vulnerability is categorized under CWE-41 (Improper Resolution of Path Equivalence), indicating a logic flaw in how the system normalizes or compares paths, leading to security bypass. Given the affected product is Windows 10 Version 1809, which is an older Windows 10 release, many organizations may have already moved to newer versions, but legacy systems remain at risk. The vulnerability's medium CVSS score (4.3) reflects its limited impact scope and the requirement for user interaction, though the network attack vector increases its risk profile compared to local vulnerabilities.

For European organizations, this vulnerability poses a moderate risk primarily to legacy systems still running Windows 10 Version 1809. The ability to bypass security zone restrictions can enable attackers to deliver malicious content or scripts that would otherwise be blocked, potentially leading to unauthorized disclosure of sensitive information or exposure to further exploitation chains. While the vulnerability does not directly affect system integrity or availability, the confidentiality impact could lead to data leaks or unauthorized access to internal network resources if combined with social engineering or phishing campaigns. Organizations in sectors with high regulatory requirements for data protection, such as finance, healthcare, and government, may face compliance risks if sensitive data confidentiality is compromised. The requirement for user interaction means that effective user awareness and training can reduce exploitation likelihood. However, the network attack vector means that attackers can target users remotely, increasing the attack surface. Since no known exploits are currently in the wild, the immediate threat is low, but the vulnerability should be addressed promptly to prevent future exploitation, especially in environments where legacy Windows 10 systems remain operational.

1. Upgrade affected systems to a supported and fully patched version of Windows 10 or later, as Windows 10 Version 1809 is out of mainstream support and may not receive security updates. 2. Implement network-level protections such as web filtering and URL reputation services to block access to known malicious URLs and reduce the risk of users accessing crafted malicious paths. 3. Enforce strict application whitelisting and use endpoint protection solutions capable of detecting suspicious script execution or abnormal network activity related to URL handling. 4. Conduct targeted user awareness training focusing on the risks of interacting with unsolicited links or network resources, emphasizing caution with unknown or unexpected URLs. 5. Monitor network traffic and endpoint logs for unusual access patterns or attempts to exploit URL handling mechanisms. 6. If upgrading is not immediately feasible, consider applying group policy settings to restrict or disable legacy URL zone mappings or reduce the trust level of network locations. 7. Stay alert for official patches or advisories from Microsoft and apply them promptly once available.