CVE-2025-54915 is a vulnerability classified as CWE-843 (Access of Resource Using Incompatible Type, also known as 'Type Confusion') found in the Windows Defender Firewall Service on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability allows an authorized local attacker to elevate their privileges on the affected system. The flaw arises due to improper handling of resource types within the firewall service, leading to type confusion. This can cause the system to access or manipulate resources under incorrect assumptions about their type, potentially enabling the attacker to execute code or perform actions with higher privileges than originally granted. The CVSS v3.1 base score is 6.7, indicating a medium severity level. The vector string (AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H) shows that the attack requires local access with low complexity, but high privileges are needed to exploit it, no user interaction is required, and the impact on confidentiality, integrity, and availability is high. No known exploits are currently reported in the wild, and no patches or fixes have been linked yet. The vulnerability was reserved on July 31, 2025, and published on September 9, 2025. Given it affects Windows 10 Version 1809, which is an older release, many organizations may still have systems running this version, especially in environments with legacy dependencies or delayed upgrade cycles. The Windows Defender Firewall Service is a critical component for network security, and exploitation could allow attackers to bypass security controls or gain administrative control, severely compromising system security.

For European organizations, this vulnerability poses a significant risk, particularly in sectors relying on Windows 10 Version 1809 in their infrastructure, such as government agencies, healthcare, manufacturing, and critical infrastructure. Successful exploitation could lead to unauthorized privilege escalation, allowing attackers to disable security controls, access sensitive data, or deploy further malware. This could result in data breaches, operational disruptions, or compliance violations under regulations like GDPR. Since the vulnerability requires local access and high privileges, the initial attack vector might be through compromised user accounts or insider threats. However, once exploited, the attacker could gain full control over the affected system, potentially moving laterally within networks. The lack of a patch increases the window of exposure, and the absence of known exploits in the wild currently reduces immediate risk but does not eliminate it. Organizations with legacy systems or delayed patch management are especially vulnerable. The impact on confidentiality, integrity, and availability is high, making this a critical concern for maintaining secure and compliant IT environments in Europe.

1. Immediate mitigation should focus on identifying and isolating systems running Windows 10 Version 1809 to assess exposure. 2. Apply any available security updates or patches from Microsoft as soon as they are released; monitor Microsoft security advisories closely. 3. Implement strict access controls and monitoring on systems with Windows Defender Firewall Service to detect unusual privilege escalation attempts. 4. Employ application whitelisting and endpoint detection and response (EDR) solutions to identify and block suspicious activities related to privilege escalation. 5. Restrict local administrative privileges to the minimum necessary and enforce the principle of least privilege to reduce the risk of exploitation. 6. Conduct regular audits of user accounts and permissions to identify and remediate excessive privileges. 7. Consider upgrading affected systems to a more recent, supported Windows version where this vulnerability is not present. 8. Use network segmentation to limit lateral movement if a system is compromised. 9. Educate IT staff and users about the risks of local privilege escalation and the importance of reporting suspicious behavior. 10. Prepare incident response plans specifically addressing privilege escalation scenarios to enable rapid containment and remediation.