CVE-2026-20924 is a use-after-free vulnerability classified under CWE-416 found in Windows Management Services on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw arises when the system incorrectly manages memory, freeing an object while it is still in use, which can be exploited by an authorized local attacker to execute arbitrary code with elevated privileges. This vulnerability allows privilege escalation from a low-privileged user to higher privileges, potentially SYSTEM level, without requiring user interaction. The CVSS v3.1 score of 7.8 reflects a high severity due to its impact on confidentiality, integrity, and availability, combined with the complexity of exploitation and the requirement for local access with some privileges. The vulnerability is notable for its scope, as it affects a widely deployed Windows 10 version still in use in many enterprise environments. Although no public exploits are currently known, the vulnerability's nature makes it a significant risk for lateral movement and persistence within compromised networks. The absence of a patch at the time of disclosure necessitates immediate risk mitigation strategies. The vulnerability's exploitation could lead to unauthorized access to sensitive data, system manipulation, and denial of service conditions, severely impacting organizational security postures.

For European organizations, the impact of CVE-2026-20924 is substantial, especially in sectors relying on legacy Windows 10 Version 1809 systems, such as manufacturing, healthcare, and government institutions. Successful exploitation can lead to privilege escalation, enabling attackers to bypass security controls, access confidential information, manipulate system configurations, and disrupt services. This could result in data breaches, operational downtime, and compliance violations under regulations like GDPR. The local access requirement limits remote exploitation but does not eliminate risk, as insider threats or attackers with initial footholds can leverage this vulnerability to expand control. The vulnerability's potential to compromise system integrity and availability poses risks to critical infrastructure and business continuity. European organizations with insufficient patch management or those running unsupported Windows versions are particularly vulnerable. The threat also increases the attack surface for ransomware and advanced persistent threat (APT) actors targeting European entities.

1. Prioritize upgrading or patching Windows 10 Version 1809 systems as soon as Microsoft releases an official security update addressing CVE-2026-20924. 2. Restrict local access to systems running this Windows version by enforcing strict access controls and monitoring for unauthorized logins. 3. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect and prevent exploitation attempts. 4. Employ the principle of least privilege to limit user rights, reducing the potential impact of privilege escalation. 5. Conduct regular audits of user accounts and privileges to identify and remove unnecessary elevated permissions. 6. Use network segmentation to isolate critical systems and limit lateral movement opportunities. 7. Educate IT staff and users about the risks of local privilege escalation vulnerabilities and encourage reporting of suspicious activity. 8. Maintain up-to-date backups and incident response plans to mitigate potential damage from exploitation. 9. Monitor security advisories from Microsoft and threat intelligence sources for updates or emerging exploit information.