CVE-2025-54104 is a local privilege escalation vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, or type confusion) affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability exists within the Windows Defender Firewall Service, where the service improperly handles resource types, allowing an attacker with authorized local access and high privileges to confuse the system about the type of resource being accessed. This type confusion can lead to the attacker gaining elevated privileges beyond their current authorization level. The vulnerability does not require user interaction and can be exploited locally, meaning the attacker must already have some level of access to the system but can then escalate privileges to potentially full system control. The CVSS v3.1 base score is 6.7, reflecting medium severity, with high impact on confidentiality, integrity, and availability (all rated high), low attack complexity, and requiring privileges but no user interaction. No public exploits or patches are currently available, but the vulnerability is publicly disclosed and assigned a CVE ID. This vulnerability is particularly relevant for organizations still running Windows 10 Version 1809, which is an older, out-of-support version, often found in legacy environments. Exploitation could allow attackers to bypass security controls, install persistent malware, or disrupt system operations by leveraging the firewall service's elevated privileges. The vulnerability highlights the risks of running unsupported OS versions and the importance of timely patching or upgrading.

For European organizations, this vulnerability poses a significant risk especially to those maintaining legacy Windows 10 Version 1809 systems, which may still be present in industrial, governmental, or critical infrastructure environments. Successful exploitation could allow attackers with local access to escalate privileges, potentially leading to full system compromise. This could result in unauthorized access to sensitive data, disruption of network security controls (since the firewall service is involved), and the ability to deploy persistent malware or ransomware. The impact is amplified in environments where endpoint security relies heavily on Windows Defender Firewall for network protection. Additionally, organizations in sectors with strict regulatory requirements (e.g., finance, healthcare, energy) could face compliance violations if such vulnerabilities are exploited. The lack of known exploits in the wild currently reduces immediate risk, but the medium severity score and high impact on confidentiality, integrity, and availability mean that the threat should be taken seriously. The vulnerability also underscores the risks of running outdated OS versions that no longer receive mainstream support or security updates.

1. Upgrade affected systems from Windows 10 Version 1809 to a supported, fully patched version of Windows 10 or Windows 11 to eliminate the vulnerability. 2. If upgrading is not immediately possible, implement strict access controls to limit local user privileges and restrict access to systems running the vulnerable OS version. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for suspicious privilege escalation attempts. 4. Isolate legacy systems from critical network segments to reduce the attack surface and limit lateral movement. 5. Monitor Windows Defender Firewall Service logs and system event logs for unusual activity indicative of exploitation attempts. 6. Follow Microsoft security advisories closely for the release of patches or mitigations specific to CVE-2025-54104 and apply them promptly. 7. Conduct regular vulnerability assessments and penetration tests focusing on privilege escalation vectors. 8. Educate system administrators and users about the risks of running unsupported OS versions and the importance of timely updates.