CVE-2025-54104 is a vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, commonly known as 'Type Confusion') affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw exists within the Windows Defender Firewall Service, a critical component responsible for managing network traffic filtering and security policies on the host. The vulnerability allows an authorized local attacker—meaning the attacker must have some level of legitimate access to the system—to exploit a type confusion error. This occurs when the software incorrectly interprets the type of a resource or object, leading to unintended behavior. In this case, the attacker can leverage this flaw to elevate their privileges on the affected system, potentially gaining higher-level access than originally permitted. The CVSS v3.1 base score is 6.7, indicating a medium severity level. The vector details specify that the attack requires local access (AV:L), low attack complexity (AC:L), and high privileges (PR:H) but no user interaction (UI:N). The impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), meaning successful exploitation could lead to full system compromise. No known exploits are currently reported in the wild, and no patches or mitigation links have been published yet. The vulnerability was reserved in mid-July 2025 and published in early September 2025, indicating recent discovery and disclosure. Given the affected product is Windows 10 Version 1809, which is an older release, systems still running this version are at risk if unpatched. The Windows Defender Firewall Service is integral to system security, so exploitation could undermine the host's defense mechanisms and allow attackers to bypass security controls.

For European organizations, this vulnerability poses a significant risk primarily to endpoints and servers still operating on Windows 10 Version 1809. Although the attack requires local access and high privileges, the ability to elevate privileges further can enable attackers to execute arbitrary code with SYSTEM-level rights, disable security controls, or move laterally within networks. This can lead to data breaches, disruption of critical services, or deployment of ransomware and other malware. Organizations in sectors with stringent regulatory requirements (e.g., finance, healthcare, critical infrastructure) may face compliance issues if this vulnerability is exploited. The lack of known exploits in the wild currently reduces immediate risk, but the medium severity and high impact on confidentiality, integrity, and availability mean that targeted attacks or insider threats could leverage this flaw. Additionally, legacy systems or those with delayed patching cycles common in some European enterprises increase exposure. The vulnerability could also be used as a stepping stone in multi-stage attacks, complicating incident response and forensic investigations.

1. Immediate inventory and identification of all systems running Windows 10 Version 1809 within the organization. 2. Prioritize upgrading or patching affected systems as soon as Microsoft releases an official security update addressing CVE-2025-54104. 3. Until patches are available, restrict local administrative access to trusted personnel only and enforce the principle of least privilege to minimize the number of users with high-level rights. 4. Implement enhanced monitoring and alerting for unusual privilege escalation attempts or suspicious activity related to the Windows Defender Firewall Service. 5. Use application whitelisting and endpoint detection and response (EDR) solutions to detect and block exploitation attempts. 6. Conduct user awareness training to reduce insider threat risks and ensure that local accounts are secured with strong authentication mechanisms. 7. Consider network segmentation to limit lateral movement if a system is compromised. 8. Regularly review and harden firewall and security policies to reduce attack surface. 9. Maintain up-to-date backups and incident response plans to mitigate potential impact if exploitation occurs.