CVE-2025-54915 is a vulnerability classified under CWE-843 (Access of Resource Using Incompatible Type, commonly known as type confusion) affecting the Windows Defender Firewall Service in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This flaw allows an authorized attacker with local access and existing privileges to exploit the type confusion bug to elevate their privileges on the affected system. Type confusion occurs when a program accesses a resource assuming it is of one type, but it is actually of another, leading to undefined behavior that attackers can leverage to manipulate memory or control flow. In this case, the Windows Defender Firewall Service improperly handles resource types, enabling privilege escalation without requiring user interaction. The CVSS v3.1 base score is 6.7, indicating a medium severity level, with attack vector local (AV:L), low attack complexity (AC:L), high privileges required (PR:H), no user interaction (UI:N), and impacts on confidentiality, integrity, and availability (all high). Although no known exploits are currently reported in the wild, the vulnerability's presence in a core security component like the firewall service makes it a significant concern. No patches have been linked yet, but organizations should anticipate updates from Microsoft. The vulnerability's exploitation could allow attackers to bypass security controls, execute arbitrary code with elevated privileges, and compromise system integrity and confidentiality.

For European organizations, this vulnerability poses a risk primarily to systems still running Windows 10 Version 1809, which, despite being an older release, may remain in use in some enterprises due to legacy application dependencies or delayed upgrade cycles. Successful exploitation could lead to attackers gaining elevated privileges locally, enabling them to disable security controls, access sensitive data, or deploy further malware. This is particularly critical for sectors with high-value targets such as government agencies, financial institutions, healthcare providers, and critical infrastructure operators. The impact extends to confidentiality breaches, integrity violations through unauthorized system modifications, and availability disruptions if attackers disable security services or cause system instability. Since the attack requires local access and high privileges, insider threats or attackers who have already compromised lower-privileged accounts pose the greatest risk. The lack of known exploits in the wild provides a window for proactive defense, but organizations must act swiftly to prevent potential future exploitation.

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. Restrict local administrative privileges to only trusted personnel and implement the principle of least privilege to reduce the risk of privilege escalation. 3. Monitor and audit local user activities, especially those involving firewall service interactions or attempts to escalate privileges. 4. Employ application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. 5. Harden local access controls by disabling or limiting remote desktop and other local access methods where not necessary. 6. Prepare to deploy Microsoft patches promptly once released, and test updates in controlled environments before wide deployment. 7. Conduct regular vulnerability assessments and penetration testing focusing on privilege escalation vectors. 8. Educate IT staff about the risks associated with legacy operating systems and encourage timely upgrades.