CVE-2026-20938 is a vulnerability classified under CWE-822 (Untrusted Pointer Dereference) found in the Windows Virtualization-Based Security (VBS) Enclave component of Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). VBS enclaves are designed to provide isolated, secure environments within the OS to protect sensitive operations and data. The vulnerability arises when the system dereferences pointers that have not been properly validated or sanitized, allowing an attacker with authorized local access to manipulate these pointers. This manipulation can lead to privilege escalation, enabling the attacker to gain higher system privileges than originally granted. The CVSS v3.1 score of 7.8 reflects a high severity, with attack vector being local (AV:L), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), and impacting confidentiality, integrity, and availability (C:H/I:H/A:H). The scope remains unchanged (S:U), meaning the vulnerability affects only the vulnerable component and not other system components. Although no exploits are currently known in the wild, the vulnerability's nature and impact make it a critical concern for organizations relying on Windows 11's VBS for security. The lack of a patch at the time of publication necessitates proactive mitigation and monitoring. This vulnerability could be exploited by malicious insiders or malware that has gained local access, potentially leading to full system compromise.

For European organizations, this vulnerability poses a significant risk to systems running Windows 11 Version 25H2, particularly those utilizing VBS for enhanced security. Successful exploitation can lead to full privilege escalation, undermining the security guarantees of VBS enclaves and potentially exposing sensitive data or allowing persistent malware installation. This could impact confidentiality by exposing protected data, integrity by allowing unauthorized changes, and availability by enabling denial-of-service conditions or system instability. Critical sectors such as finance, healthcare, government, and critical infrastructure that rely on Windows 11 and VBS for security hardening are at heightened risk. The local attack vector means that insider threats or malware that has already breached perimeter defenses could leverage this vulnerability to escalate privileges and move laterally within networks. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as exploit development could follow soon after disclosure. European organizations should consider this vulnerability a priority for risk assessment and remediation planning.

Until an official patch is released by Microsoft, European organizations should implement several specific mitigations: 1) Restrict local administrative access strictly to trusted personnel and systems to reduce the attack surface. 2) Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious privilege escalation attempts. 3) Harden VBS configurations and ensure that only necessary services and applications run within the enclave environment. 4) Conduct regular audits of local accounts and privileges to detect unauthorized changes. 5) Use network segmentation to limit lateral movement opportunities if an attacker gains local access. 6) Prepare for rapid deployment of the official patch by identifying all affected Windows 11 Version 25H2 systems in the environment. 7) Educate users and administrators about the risk of local privilege escalation and the importance of reporting unusual system behavior. 8) Monitor security advisories from Microsoft and trusted sources for updates and exploit reports. These targeted actions go beyond generic advice by focusing on minimizing local access and monitoring enclave-related activities.