CVE-2026-21223 is a vulnerability categorized under CWE-269 (Improper Privilege Management) affecting the Microsoft Edge Elevation Service in the Chromium-based Microsoft Edge browser, specifically version 1.0.0.0. The vulnerability arises because the Elevation Service exposes a privileged COM interface (IElevatorEdge) that fails to properly validate the privileges of the calling process. A local user without administrative rights can invoke the interface method LaunchUpdateCmdElevatedAndWait, which causes the Elevation Service to execute update commands with LocalSystem privileges. This escalation allows the attacker to modify protected registry keys under HKLM\SYSTEM\CurrentControlSet\Control\DeviceGuard, effectively enabling or disabling Windows Virtualization-Based Security (VBS). VBS is a critical security feature that leverages hardware virtualization to isolate and protect key system components, including Credential Guard, Hypervisor-protected Code Integrity (HVCI), and the Secure Kernel. Disabling VBS undermines these protections, potentially allowing credential theft, code integrity bypass, and kernel-level attacks. The vulnerability has a CVSS 3.1 base score of 5.1, reflecting medium severity, with attack vector local, low attack complexity, no privileges required, and no user interaction needed. No patches or known exploits are currently reported. The flaw's exploitation scope is limited to local users but can have a broad impact on system security by disabling foundational protection mechanisms.

For European organizations, this vulnerability poses a significant risk to endpoint security, especially in environments that rely on Windows Virtualization-Based Security to protect sensitive data and maintain system integrity. Disabling VBS can lead to the bypass of Credential Guard, increasing the risk of credential theft and lateral movement within corporate networks. The weakening of Hypervisor-protected Code Integrity and the Secure Kernel can allow attackers to execute unauthorized code at the kernel level, potentially leading to persistent and stealthy compromises. Organizations in sectors with high security requirements, such as finance, healthcare, and critical infrastructure, may face increased exposure to advanced persistent threats if this vulnerability is exploited. Additionally, the local attack vector means that insider threats or attackers who gain limited local access can escalate privileges and disable critical security features, complicating incident response and recovery efforts.

To mitigate this vulnerability, organizations should first ensure that all systems are updated with the latest security patches from Microsoft once they become available. Until patches are released, restrict local user access to systems where possible, especially limiting standard user accounts from executing untrusted code or accessing the Microsoft Edge Elevation Service. Employ application control policies to prevent unauthorized invocation of COM interfaces related to the Elevation Service. Monitor registry changes under HKLM\SYSTEM\CurrentControlSet\Control\DeviceGuard for unauthorized modifications indicative of VBS being disabled. Implement endpoint detection and response (EDR) solutions capable of detecting suspicious privilege escalation attempts and registry tampering. Additionally, enforce the principle of least privilege rigorously and conduct regular audits of local user permissions. Consider deploying additional layers of security such as network segmentation and multi-factor authentication to reduce the risk of local attackers gaining initial access.