CVE-2026-20938 is a vulnerability identified in Microsoft Windows 11 Version 25H2 (build 10.0.26200.0) that affects the Virtualization-Based Security (VBS) Enclave, a security feature designed to isolate sensitive processes and data from the rest of the operating system. The vulnerability is classified as CWE-822: Untrusted Pointer Dereference, which occurs when the software dereferences a pointer that can be influenced by an attacker, leading to undefined behavior or security breaches. In this case, an authorized local attacker can exploit this flaw to elevate their privileges within the system. The attack vector requires local access with low complexity (AV:L, AC:L, PR:L), and no user interaction is needed (UI:N). The vulnerability impacts confidentiality, integrity, and availability (C:H, I:H, A:H), meaning an attacker could gain unauthorized access to sensitive information, modify system state, or disrupt system operations. The scope is unchanged (S:U), indicating the vulnerability affects only the vulnerable component without extending to other system components. Although there are no known exploits in the wild, the vulnerability's presence in a widely deployed OS version and its impact on a critical security feature make it a significant risk. The lack of available patches at the time of publication necessitates immediate attention to mitigation strategies. The vulnerability was reserved on December 4, 2025, and published on January 13, 2026, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a substantial risk, particularly for enterprises and government agencies that rely on Windows 11 25H2 and utilize VBS for enhanced security. Exploitation could allow attackers with local access—such as malicious insiders or attackers who have compromised lower-privileged accounts—to escalate privileges, potentially gaining administrative control over affected systems. This could lead to unauthorized access to sensitive data, disruption of critical services, and the ability to bypass security controls enforced by VBS. Sectors such as finance, healthcare, energy, and public administration, which often deploy virtualization-based security to protect sensitive workloads, are especially vulnerable. The vulnerability could facilitate lateral movement within networks, increasing the risk of widespread compromise. Given the high adoption rate of Windows 11 in Europe and the strategic importance of securing endpoints, the threat could have broad operational and reputational impacts if exploited.

1. Monitor Microsoft security advisories closely and apply official patches or updates as soon as they become available to remediate the vulnerability. 2. Until patches are released, restrict local access to systems running Windows 11 25H2, limiting user privileges and enforcing strict access controls to reduce the risk of exploitation by unauthorized users. 3. Implement enhanced endpoint detection and response (EDR) solutions capable of identifying suspicious privilege escalation attempts and anomalous behavior within VBS enclaves. 4. Conduct regular audits of local user accounts and remove or disable unnecessary accounts with local privileges. 5. Employ application control policies to limit execution of unauthorized code that could exploit the vulnerability. 6. Educate IT and security teams about the vulnerability specifics to ensure rapid detection and response to potential exploitation attempts. 7. Consider deploying additional layers of security such as multi-factor authentication for local logins and network segmentation to contain potential breaches.