CVE-2025-21213 is a security vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) that involves improper access control related to the Secure Boot security feature. Secure Boot is a critical security mechanism designed to ensure that only trusted software is loaded during the system startup process, protecting against boot-level malware and rootkits. The vulnerability is classified under CWE-284, which pertains to improper access control, indicating that the Secure Boot feature can be bypassed due to insufficient enforcement of access restrictions. The CVSS v3.1 base score is 4.6 (medium severity), with the vector indicating that the attack requires physical access (Attack Vector: Physical), low attack complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality but no impact on integrity or availability. This suggests that an attacker with physical access to the device could exploit this vulnerability to bypass Secure Boot protections, potentially gaining unauthorized access to sensitive information stored on the device or compromising confidentiality. However, the vulnerability does not affect system integrity or availability directly, and no known exploits are currently reported in the wild. No patches are listed yet, indicating that mitigation or fixes may still be pending or under development. The vulnerability was reserved in December 2024 and published in January 2025, reflecting recent discovery and disclosure.

For European organizations, this vulnerability poses a risk primarily to devices running Windows 10 Version 1809, which, although an older version, may still be in use in certain environments due to legacy application dependencies or delayed upgrade cycles. The Secure Boot bypass could allow attackers with physical access—such as insiders, contractors, or attackers who gain temporary physical control of devices—to circumvent boot-level security controls. This could lead to unauthorized access to confidential data, potentially exposing sensitive corporate or personal information. While the vulnerability does not directly compromise system integrity or availability, the breach of confidentiality could have significant regulatory and reputational consequences, especially under GDPR requirements for data protection. Organizations with high-value intellectual property, sensitive customer data, or critical infrastructure components could be particularly impacted. The physical access requirement limits remote exploitation, but the risk remains in scenarios involving device theft, loss, or insider threats.

Given the physical access requirement, mitigation should focus on physical security controls and device management policies. Organizations should ensure strict physical access controls to devices, including secure storage, surveillance, and access logging. Full disk encryption solutions (e.g., BitLocker) should be enforced with strong authentication to protect data even if Secure Boot is bypassed. Devices running Windows 10 Version 1809 should be prioritized for upgrade to supported, patched versions of Windows 10 or Windows 11 where this vulnerability is addressed. Until patches are available, organizations should implement endpoint detection and response (EDR) solutions to monitor for suspicious boot or firmware activities. Additionally, disabling boot from external media in BIOS/UEFI settings and enforcing strong BIOS/UEFI passwords can reduce exploitation risk. Regular audits of device firmware and boot configurations can help detect unauthorized changes. Employee training on the risks of physical device compromise and secure handling procedures is also recommended.