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. A TOCTOU race condition occurs when a system checks a condition and then uses the result of that check at a later time, during which the state may have changed, leading to a security flaw. In this case, the vulnerability allows an unauthorized attacker with physical access to the device to bypass BitLocker's security protections. BitLocker is designed to protect data by encrypting entire volumes, preventing unauthorized access to data at rest. The flaw arises because the race condition can be exploited to manipulate the timing between the security check and the use of the checked resource, effectively bypassing the encryption safeguards. The vulnerability affects Windows 10 Version 1809 (build 10.0.17763.0), an older but still in-use version of Windows 10. The CVSS v3.1 score is 6.8, indicating a medium severity level, with the vector indicating that the attack requires physical access (AV:P), no privileges (PR:N), no user interaction (UI:N), and impacts confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits are currently in the wild, and no patches have been linked yet. The vulnerability was reserved in May 2025 and published in July 2025. The CWE classification is CWE-367, which corresponds to TOCTOU race conditions. This vulnerability is significant because it undermines BitLocker's core purpose of protecting data confidentiality on Windows devices, especially in scenarios where physical device security is critical.

For European organizations, this vulnerability poses a substantial risk, particularly for sectors relying heavily on data confidentiality and regulatory compliance, such as finance, healthcare, government, and critical infrastructure. Since the attack requires physical access, the threat is most relevant in environments where devices may be lost, stolen, or accessed by unauthorized personnel, such as mobile workforces or shared office spaces. Successful exploitation could lead to unauthorized data disclosure, data tampering, and potential disruption of services due to compromised system integrity and availability. This could result in violations of GDPR and other data protection regulations, leading to legal and financial repercussions. Additionally, the ability to bypass BitLocker undermines trust in endpoint security, potentially exposing sensitive intellectual property and personal data. The medium severity rating suggests that while exploitation is not trivial, the consequences of a successful attack are severe, especially given the widespread use of Windows 10 1809 in enterprise environments that have not upgraded to newer versions.

Organizations should prioritize upgrading affected systems from Windows 10 Version 1809 to a more recent, supported Windows version where this vulnerability is addressed. Since no patches are currently linked, applying the latest cumulative updates and security patches from Microsoft as they become available is critical. Physical security controls must be enhanced to prevent unauthorized access to devices, including secure storage, device tracking, and endpoint protection solutions that detect tampering. Employing full disk encryption with multi-factor authentication and hardware-based security modules (e.g., TPM) can add layers of defense. Regular audits of device inventory and access logs can help detect potential exploitation attempts. Additionally, organizations should implement strict policies for device handling, especially for laptops and portable devices, and consider disabling or restricting BitLocker recovery key access to minimize risk. Incident response plans should be updated to include scenarios involving physical device compromise and encryption bypass.