CVE-2026-20815 is a race condition vulnerability classified under CWE-362, found in the Capability Access Management Service (camsvc) component of Microsoft Windows Server 2025 Server Core installations, specifically version 10.0.26100.0. The flaw arises from improper synchronization when multiple threads or processes concurrently access shared resources, leading to inconsistent or unexpected states. An authorized attacker with local access but low privileges can exploit this race condition to elevate their privileges on the system, potentially gaining administrative rights. The vulnerability does not require user interaction, increasing the risk of automated or stealthy exploitation once local access is obtained. The CVSS v3.1 score of 7.0 reflects high severity, with impacts on confidentiality, integrity, and availability, though exploitation complexity is high due to the need for precise timing and local access. No public exploits are known at this time, but the vulnerability poses a significant risk to environments relying on Windows Server 2025 Server Core, especially those with multi-tenant or shared resource scenarios. The absence of patches at the time of publication necessitates proactive mitigation and monitoring by administrators.

For European organizations, this vulnerability could lead to unauthorized privilege escalation on critical server infrastructure, compromising sensitive data and operational continuity. Attackers gaining elevated privileges could deploy malware, exfiltrate data, disrupt services, or pivot to other network segments. Sectors such as finance, healthcare, government, and critical infrastructure, which often deploy Windows Server Core for its reduced attack surface and performance benefits, are particularly at risk. The local access requirement limits remote exploitation but insider threats or compromised accounts could leverage this flaw. The potential for full system compromise threatens confidentiality, integrity, and availability, impacting compliance with regulations like GDPR and NIS Directive. Disruption or data breaches could result in financial losses, reputational damage, and regulatory penalties for affected organizations.

Organizations should implement strict access controls to limit local user accounts and enforce the principle of least privilege to reduce the attack surface. Monitoring and logging of privilege escalation attempts and unusual process behaviors should be enhanced to detect exploitation attempts early. Network segmentation can help contain potential breaches originating from compromised servers. Administrators should prioritize patch management and apply security updates from Microsoft as soon as they become available for Windows Server 2025 Server Core installations. Until patches are released, consider temporary workarounds such as disabling or restricting the Capability Access Management Service if feasible without impacting critical operations. Conduct regular security audits and penetration testing focused on privilege escalation vectors. Employ endpoint detection and response (EDR) solutions capable of identifying race condition exploitation patterns. Finally, educate system administrators about this vulnerability to ensure rapid response and mitigation.