CVE-2025-54915 is a vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, or type confusion) found in the Windows Defender Firewall Service on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This flaw allows an attacker who already has authorized local access to the system to exploit the type confusion bug to elevate their privileges. Type confusion occurs when a program accesses a resource using an incorrect or incompatible data type, leading to unpredictable behavior and potential security breaches. In this case, the Windows Defender Firewall Service improperly handles certain data types, enabling an attacker to manipulate the service to gain higher privileges than originally granted. The CVSS v3.1 base score is 6.7, indicating a medium severity level, with the vector showing that the attack requires local access (AV:L), low attack complexity (AC:L), high privileges required (PR:H), no user interaction (UI:N), unchanged scope (S:U), and impacts confidentiality, integrity, and availability (C:H/I:H/A:H). The exploitability is moderate since the attacker must have local authorized access but does not require user interaction, making it a significant risk in environments where multiple users have local access or where initial footholds have been established. No known exploits are currently reported in the wild, and no patches have been linked at the time of publication, emphasizing the need for proactive mitigation. The vulnerability affects legacy Windows 10 systems, which remain in use in many enterprise environments, especially where upgrading is delayed due to compatibility or operational constraints.

For European organizations, the impact of CVE-2025-54915 can be substantial, particularly in sectors relying on legacy Windows 10 Version 1809 systems such as manufacturing, healthcare, government, and critical infrastructure. Successful exploitation allows an attacker with local access to escalate privileges, potentially gaining SYSTEM-level control. This can lead to unauthorized access to sensitive data, disruption of services, and the ability to deploy further malware or ransomware with elevated rights. The compromise of firewall services could also weaken network defenses, enabling lateral movement within networks. Since many European enterprises maintain legacy systems for compatibility reasons, the risk of exploitation increases. Additionally, regulatory frameworks like GDPR impose strict requirements on data protection, and a breach resulting from this vulnerability could lead to significant legal and financial penalties. The absence of known exploits currently reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits after public disclosure. Organizations with multi-user environments or those that allow local user access without strict controls are particularly vulnerable.

To mitigate CVE-2025-54915, European organizations should: 1) Prioritize upgrading or patching Windows 10 Version 1809 systems as soon as official patches become available from Microsoft. 2) Restrict local user access to systems running the affected OS version, enforcing strict access controls and limiting administrative privileges. 3) Implement application whitelisting and endpoint detection and response (EDR) solutions to monitor for suspicious activity related to privilege escalation attempts. 4) Harden Windows Defender Firewall Service configurations and audit firewall service logs for anomalies. 5) Employ network segmentation to limit the impact of a compromised host and reduce lateral movement opportunities. 6) Conduct regular vulnerability assessments and penetration testing focusing on privilege escalation vectors. 7) Educate IT staff and users about the risks of local privilege escalation and enforce the principle of least privilege across all systems. 8) Maintain an inventory of systems running legacy OS versions to prioritize remediation efforts effectively. These measures go beyond generic advice by focusing on controlling local access, monitoring firewall service behavior, and preparing for patch deployment.