CVE-2026-20874 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 vulnerability arises from improper synchronization when multiple threads or processes concurrently access shared resources, leading to a race condition. This flaw can be exploited by an attacker with local authorized access to elevate privileges, potentially gaining SYSTEM-level rights. The CVSS v3.1 score of 7.8 reflects a high severity, with attack vector local, requiring high attack complexity and low privileges but no user interaction. The scope is changed, indicating that the vulnerability can affect resources beyond the initially compromised component, impacting confidentiality, integrity, and availability at a high level. Although no known exploits are currently in the wild, the vulnerability poses a significant risk due to the potential for full system compromise. The lack of available patches at the time of publication necessitates immediate risk mitigation through access restrictions and monitoring. This vulnerability is particularly relevant for organizations still operating legacy Windows 10 1809 systems, which remain common in enterprise environments due to extended support lifecycles. The race condition could be triggered by malicious local processes or users exploiting timing windows in resource access, leading to privilege escalation and unauthorized control over system functions.

For European organizations, the impact of CVE-2026-20874 is substantial, especially for those relying on Windows 10 Version 1809 in critical infrastructure, government, finance, healthcare, and industrial sectors. Successful exploitation allows attackers to escalate privileges locally, potentially leading to full system compromise, data breaches, disruption of services, and lateral movement within networks. This can undermine confidentiality by exposing sensitive data, integrity by allowing unauthorized changes, and availability by enabling denial-of-service conditions or system instability. The requirement for local access limits remote exploitation but does not eliminate risk, as insider threats or compromised endpoints can serve as attack vectors. The high attack complexity reduces the likelihood of widespread automated attacks but does not preclude targeted attacks against high-value European targets. Legacy systems prevalent in some European organizations increase exposure, and the absence of patches at the time of disclosure heightens urgency for mitigation. The vulnerability could also be leveraged as a stepping stone in multi-stage attacks, amplifying its impact on organizational security posture.

1. Apply official patches from Microsoft immediately once they become available to remediate the race condition vulnerability. 2. Until patches are released, restrict local access to Windows 10 Version 1809 systems by enforcing strict user account controls and limiting administrative privileges. 3. Implement application whitelisting and endpoint protection solutions to detect and block suspicious local processes attempting privilege escalation. 4. Monitor system logs and Windows Management Services activity for unusual behavior indicative of race condition exploitation attempts. 5. Conduct regular audits of user permissions and remove unnecessary local accounts to reduce attack surface. 6. Consider upgrading affected systems to a supported and patched Windows version to eliminate exposure to legacy vulnerabilities. 7. Employ network segmentation to isolate critical systems running Windows 10 1809, minimizing lateral movement opportunities. 8. Educate IT staff and users about the risks of local privilege escalation and the importance of reporting anomalies promptly. These measures go beyond generic advice by focusing on controlling local access vectors, proactive monitoring, and system lifecycle management tailored to this specific vulnerability.