CVE-2025-54094 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 system. The vulnerability allows an authorized local attacker to exploit a type confusion error, where the system incorrectly accesses or manipulates a resource using an incompatible data type. This can lead to unexpected behavior, including memory corruption or privilege escalation. Specifically, the attacker can leverage this flaw to elevate their privileges on the affected system, potentially gaining SYSTEM-level access from a lower privileged context. The CVSS v3.1 base score is 6.7 (medium severity), with the vector indicating local attack vector (AV:L), low attack complexity (AC:L), required high privileges (PR:H), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits are currently reported in the wild, and no patches or mitigation links have been provided yet. The vulnerability was reserved in mid-July 2025 and published in early September 2025, indicating a recent disclosure. The lack of user interaction and the high impact on all security properties make this a significant concern for systems still running this older Windows 10 version, especially in environments where local access is possible for attackers or malicious insiders.

For European organizations, the impact of CVE-2025-54094 can be substantial, particularly in sectors where Windows 10 Version 1809 remains in use, such as legacy industrial control systems, government agencies, or enterprises with delayed upgrade cycles. Successful exploitation allows an attacker with local access and already elevated privileges to escalate to SYSTEM-level privileges, effectively gaining full control over the affected machine. This can lead to unauthorized data access, modification, or deletion, disruption of critical services, and potential lateral movement within corporate networks. Confidentiality, integrity, and availability of sensitive data and systems could be severely compromised. Given the firewall service is involved, attackers might also manipulate network filtering rules to facilitate further attacks or evade detection. Although exploitation requires high privileges initially, insider threats or attackers who have compromised lower privileged accounts could leverage this vulnerability to deepen their foothold. The absence of known exploits in the wild reduces immediate risk but does not eliminate it, especially as threat actors often develop exploits post-disclosure. Organizations in Europe with compliance requirements such as GDPR must consider the risk of data breaches resulting from such privilege escalations, which could lead to regulatory penalties and reputational damage.

To mitigate CVE-2025-54094, European organizations should prioritize upgrading affected systems to a supported and patched Windows version as soon as Microsoft releases an official security update. Until patches are available, organizations should: 1) Restrict local access to systems running Windows 10 Version 1809, enforcing strict physical and logical access controls to minimize the risk of local exploitation. 2) Employ application whitelisting and endpoint protection solutions to detect and block suspicious activities indicative of privilege escalation attempts. 3) Monitor Windows Defender Firewall Service logs and system event logs for anomalous behavior or errors that could signal exploitation attempts. 4) Harden user privilege assignments by applying the principle of least privilege, ensuring users do not have unnecessary administrative rights. 5) Use network segmentation to limit lateral movement opportunities if an attacker gains elevated privileges on one machine. 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 vulnerabilities and the importance of timely patching. These targeted steps go beyond generic advice by focusing on controlling local access, monitoring firewall service behavior, and minimizing privilege exposure in legacy Windows environments.