CVE-2025-27735 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically affecting the Windows Virtualization-Based Security (VBS) Enclave component. The vulnerability is categorized under CWE-345, which pertains to insufficient verification of data authenticity. In this context, the VBS Enclave fails to adequately verify the authenticity of data it processes, allowing an attacker with authorized local access and high privileges to bypass certain security features. The vulnerability does not require user interaction but does require that the attacker already has elevated privileges (PR:H). The CVSS v3.1 base score is 6.0, indicating a medium severity level. The attack vector is local (AV:L), meaning the attacker must have local access to the system. The vulnerability impacts confidentiality and integrity, allowing the attacker to potentially manipulate or access sensitive data protected by the VBS enclave, but it does not affect availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is significant because VBS enclaves are designed to provide a hardware-isolated environment to protect sensitive operations and data, so bypassing these protections undermines the security guarantees of the system. Since Windows 10 Version 1809 is an older release, many organizations may have already migrated to newer versions, but legacy systems still in use remain at risk. The lack of user interaction and the requirement for high privileges suggest that the vulnerability could be exploited by malicious insiders or through privilege escalation chains. Overall, this vulnerability represents a moderate risk that could facilitate further compromise of sensitive information on affected systems.

For European organizations, the impact of CVE-2025-27735 could be significant in environments where Windows 10 Version 1809 is still operational, especially in sectors relying on VBS for enhanced security, such as government, finance, healthcare, and critical infrastructure. The ability to bypass VBS enclave protections could lead to unauthorized access to confidential data, intellectual property theft, or manipulation of security-critical processes. This undermines trust in endpoint security and could facilitate lateral movement or persistence by attackers within networks. Although the vulnerability requires local high-privilege access, it could be leveraged in combination with other vulnerabilities or insider threats to escalate attacks. Organizations with compliance obligations under GDPR and other data protection regulations may face increased risk of data breaches and associated penalties if this vulnerability is exploited. The absence of known exploits in the wild provides some immediate relief, but the medium severity rating and the critical role of VBS in securing Windows endpoints mean that European organizations should prioritize mitigation to prevent potential exploitation.

1. Upgrade affected systems to a supported and updated version of Windows 10 or Windows 11 where this vulnerability is patched or not present. 2. Restrict local administrative privileges to the minimum necessary to reduce the risk of exploitation by insiders or malware. 3. Implement strict access controls and monitoring on systems running Windows 10 Version 1809, focusing on detecting unusual privilege escalations or attempts to access VBS enclave components. 4. Employ endpoint detection and response (EDR) solutions capable of monitoring VBS-related activities and alerting on suspicious behavior. 5. Apply defense-in-depth strategies such as application whitelisting, network segmentation, and multi-factor authentication to limit the impact of a potential compromise. 6. Regularly audit and update security policies to ensure legacy systems are identified and remediated or isolated. 7. Stay informed on vendor advisories for patches or workarounds related to this CVE and apply them promptly once available.