CVE-2026-21223 is a vulnerability classified under CWE-269 (Improper Privilege Management) affecting the Microsoft Edge Chromium-based browser's Elevation Service. The service exposes a privileged COM interface, IElevatorEdge, which includes the method LaunchUpdateCmdElevatedAndWait. This method can be invoked by a standard local user without administrator privileges, causing the service to execute update commands with LocalSystem privileges. This improper validation of caller privileges allows the attacker to modify critical system registry keys under HKLM\SYSTEM\CurrentControlSet\Control\DeviceGuard, specifically those controlling Windows Virtualization-Based Security (VBS). VBS encompasses security features such as Credential Guard, Hypervisor-protected Code Integrity (HVCI), and the Secure Kernel, which protect against credential theft, kernel-level code tampering, and other advanced attacks. By disabling VBS, an attacker effectively bypasses these protections, weakening the system's security posture significantly. The vulnerability requires local access but no elevated privileges or user interaction beyond invoking the COM interface. Although no known exploits are currently in the wild, the potential for privilege escalation and security feature bypass makes this a serious threat. The vulnerability affects Microsoft Edge version 1.0.0.0 and potentially later versions if unpatched. No CVSS score has been assigned yet, indicating the need for severity assessment based on impact and exploitability factors.

For European organizations, the impact of CVE-2026-21223 is substantial, particularly for enterprises relying on Windows security features to protect sensitive data and infrastructure. Disabling VBS undermines key defenses against credential theft and kernel-level attacks, increasing the risk of lateral movement, persistence, and data breaches. Sectors such as finance, healthcare, government, and critical infrastructure, which often mandate strong endpoint security, are especially vulnerable. The ability for a non-administrator local user to escalate privileges to LocalSystem could facilitate insider threats or attacks originating from compromised user accounts. This vulnerability could also be leveraged in multi-stage attacks where initial access is gained through phishing or other means, then escalated locally to disable security features and deploy further malware. The absence of known exploits currently provides a window for mitigation, but the threat landscape could evolve rapidly once exploit code becomes available. Organizations with remote or shared workstation environments may face increased risk due to the potential for local user exploitation.

1. Monitor Microsoft security advisories closely and apply patches or updates for Microsoft Edge and Windows Elevation Service as soon as they are released. 2. Restrict local user permissions rigorously, ensuring that only trusted users have local access to systems, and limit the ability to invoke COM interfaces where possible. 3. Implement application control policies to restrict execution of unauthorized or suspicious processes that might invoke the vulnerable interface. 4. Employ endpoint detection and response (EDR) solutions to monitor registry changes, especially under HKLM\SYSTEM\CurrentControlSet\Control\DeviceGuard, and alert on modifications to VBS-related keys. 5. Use group policies or configuration management tools to enforce VBS settings and prevent unauthorized changes. 6. Conduct regular audits of local user accounts and privilege assignments to minimize the risk of insider exploitation. 7. Educate users about the risks of local privilege escalation and enforce strong physical and logical access controls to workstations. 8. Consider network segmentation to limit the spread of attacks originating from compromised local accounts.