CVE-2025-48818 is a Time-of-check Time-of-use (TOCTOU) race condition vulnerability identified in Microsoft Windows 10 Version 1809, specifically affecting the BitLocker encryption feature. The vulnerability arises due to a timing window between the verification of a security condition (time-of-check) and the execution of an operation based on that check (time-of-use). In this case, an attacker with physical access to the device can exploit this race condition to bypass BitLocker's security protections. BitLocker is designed to protect data by encrypting volumes and preventing unauthorized access, especially in scenarios involving device theft or loss. The race condition could allow an attacker to manipulate the system state or timing to gain unauthorized access to encrypted data without needing credentials or user interaction. The CVSS v3.1 base score of 6.8 reflects a medium severity level, with the vector indicating that the attack requires physical access (AV:P), has low attack complexity (AC:L), requires no privileges (PR:N), and no user interaction (UI:N). The impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), meaning successful exploitation could lead to full compromise of protected data and system integrity. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is specific to Windows 10 Version 1809 (build 10.0.17763.0), which is an older version of Windows 10, but still may be in use in some environments. The CWE-367 classification confirms the root cause as a TOCTOU race condition, a common concurrency flaw where the system state changes between check and use operations, leading to security bypasses.

For European organizations, the impact of CVE-2025-48818 can be significant, particularly for those relying on Windows 10 Version 1809 with BitLocker enabled for data protection. Successful exploitation could lead to unauthorized data access, compromising confidentiality of sensitive information such as personal data protected under GDPR, intellectual property, or critical business information. Integrity and availability could also be affected if attackers modify or disrupt encrypted volumes. The requirement for physical access limits remote exploitation but raises concerns for organizations with mobile or remote workforce using laptops or portable devices. Theft or loss of devices in transit or on-premises could lead to data breaches. This vulnerability poses a risk to sectors with high data sensitivity such as finance, healthcare, government, and critical infrastructure. Additionally, organizations in Europe must consider regulatory implications of data breaches involving encrypted data, potentially leading to fines and reputational damage. The medium severity rating suggests that while the vulnerability is serious, the exploitation complexity and physical access requirement somewhat limit widespread impact. However, legacy systems still running Windows 10 Version 1809 without upgrades or mitigations remain vulnerable.

1. Upgrade affected systems to a supported and patched version of Windows 10 or later where this vulnerability is addressed. Since no patch links are currently available, prioritize migration off Windows 10 Version 1809. 2. Enforce strict physical security controls to prevent unauthorized physical access to devices, including secure storage, device tracking, and access logging. 3. Implement full disk encryption with additional layers of security such as TPM (Trusted Platform Module) and PINs or passwords to reduce the risk of bypass through physical attacks. 4. Use endpoint detection and response (EDR) tools to monitor for suspicious activity that could indicate attempts to exploit physical access vulnerabilities. 5. Educate employees on the risks of device theft and loss, and implement policies for immediate reporting and response to such incidents. 6. Regularly audit and inventory devices running legacy Windows versions to identify and remediate vulnerable endpoints. 7. Consider hardware-based security enhancements such as secure boot and measured boot to reduce attack surface related to boot-time vulnerabilities. 8. Monitor Microsoft security advisories for official patches or workarounds and apply them promptly once available.