CVE-2025-54894 is a high-severity local privilege escalation vulnerability affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability is classified as a heap-based buffer overflow (CWE-122) within the Local Security Authority Subsystem Service (LSASS), a critical Windows component responsible for enforcing security policies and managing user authentication. The flaw allows an attacker with limited privileges (local access with low privileges) to execute a carefully crafted exploit that triggers a buffer overflow in the LSASS process heap memory. This overflow can corrupt memory, leading to arbitrary code execution with elevated privileges, potentially SYSTEM-level. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and requiring only limited privileges but no user interaction. The vulnerability does not require user interaction but does require local access with some privileges (PR:L). No known public exploits or patches are currently available, and the vulnerability was published on September 9, 2025. Given the critical role of LSASS in Windows security, exploitation could allow attackers to bypass security controls, escalate privileges, and gain persistent control over affected systems. This vulnerability is particularly concerning for environments still running Windows 10 Version 1809, which is an older release and may not be fully supported or patched in many organizations.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and government entities that continue to operate legacy Windows 10 Version 1809 systems. Successful exploitation could lead to full system compromise, enabling attackers to access sensitive data, disrupt operations, or move laterally within networks. Confidentiality is severely impacted as attackers could extract credentials or sensitive information from LSASS memory. Integrity and availability are also at risk due to potential arbitrary code execution and system instability. The local attack vector means that initial access is required, but once inside, attackers can escalate privileges to SYSTEM, bypassing many security controls. This is particularly impactful for organizations with remote or hybrid workforces where endpoint security may be weaker. Additionally, the lack of available patches increases the window of exposure. The vulnerability could be leveraged in targeted attacks against critical infrastructure, financial institutions, healthcare providers, and public sector organizations in Europe, all of which often rely on Windows 10 systems and handle sensitive data.

Given the absence of official patches, European organizations should implement layered mitigations: 1) Restrict local access to systems running Windows 10 Version 1809 by enforcing strict access controls and limiting administrative privileges. 2) Employ application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior related to LSASS exploitation attempts. 3) Enable Credential Guard and other Windows security features that isolate LSASS processes and credentials in hardware-protected environments, if supported. 4) Monitor system logs and security telemetry for signs of privilege escalation or memory corruption events. 5) Plan and prioritize upgrading or migrating systems from Windows 10 Version 1809 to supported, patched Windows versions to eliminate exposure. 6) Use network segmentation to limit lateral movement opportunities if a local compromise occurs. 7) Educate users and administrators about the risks of local privilege escalation and enforce strong endpoint security policies. These steps go beyond generic advice by focusing on access restriction, advanced detection, and proactive system upgrades.