CVE-2026-20918 is a race condition vulnerability classified under CWE-362, affecting Windows Management Services in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw arises from improper synchronization when multiple threads or processes concurrently access shared resources, leading to a race condition. This condition can be exploited by an attacker with local authorized access to elevate privileges on the affected system. The vulnerability impacts confidentiality, integrity, and availability by allowing attackers to gain higher privileges than intended, potentially leading to full system compromise. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local (AV:L), attack complexity high (AC:H), privileges required low (PR:L), no user interaction (UI:N), and scope changed (S:C). The exploitability is limited by the need for local access and complex timing conditions, but the impact is severe. No public exploit code or known active exploitation has been reported yet. The vulnerability affects a legacy Windows 10 version, which remains in use in some enterprise and industrial environments. The lack of an official patch at the time of reporting necessitates proactive mitigation. This vulnerability underscores the risks of race conditions in system services that manage critical OS functions and the importance of proper synchronization in concurrent execution contexts.

For European organizations, the impact of CVE-2026-20918 can be significant, especially for those still operating Windows 10 Version 1809 in production environments. Successful exploitation allows attackers with local access to escalate privileges, potentially gaining SYSTEM-level control. This can lead to unauthorized access to sensitive data, disruption of critical services, and lateral movement within networks. Sectors such as manufacturing, healthcare, finance, and government that rely on legacy Windows 10 systems or have limited patching capabilities are particularly vulnerable. The vulnerability could be leveraged in targeted attacks against high-value assets or critical infrastructure, increasing the risk of data breaches, operational downtime, and regulatory non-compliance under GDPR. The absence of known exploits in the wild currently reduces immediate risk, but the high severity and potential impact demand urgent attention to prevent future exploitation.

1. Prioritize upgrading or patching Windows 10 systems from version 1809 to a supported and patched version as soon as Microsoft releases an official fix. 2. Until patches are available, restrict local access to affected systems by enforcing strict access controls, limiting administrative privileges, and using network segmentation to reduce attack surface. 3. Implement application whitelisting and endpoint detection and response (EDR) solutions to monitor for unusual activity related to Windows Management Services or privilege escalation attempts. 4. Conduct regular audits of user accounts and permissions to ensure minimal privilege principles are enforced. 5. Educate IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of reporting suspicious behavior. 6. Employ system hardening techniques such as disabling unnecessary services and applying security baselines tailored for legacy Windows 10 environments. 7. Monitor security advisories from Microsoft and threat intelligence sources for updates or emerging exploit information related to this CVE.