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 from a race condition between the time a security check is performed and the time the resource or operation is used, allowing an attacker to exploit the timing gap. In this case, an unauthorized attacker with physical access to the device can bypass BitLocker's security protections by exploiting this race condition. BitLocker is designed to protect data by encrypting the entire drive, preventing unauthorized access to data at rest. However, this TOCTOU flaw undermines the integrity of the security check process, potentially allowing an attacker to access encrypted data without proper authorization. The CVSS v3.1 base score is 6.8 (medium severity), reflecting that the attack vector requires physical access (AV:P), no privileges are required (PR:N), no user interaction is needed (UI:N), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). The vulnerability affects Windows 10 Version 1809 (build 10.0.17763.0), which is an older but still in-use version of Windows 10. There are no known exploits in the wild at the time of publication, and no official patches have been linked yet. The vulnerability is categorized under CWE-367, which relates to TOCTOU race conditions, a class of bugs that occur when a system checks a condition and then uses a resource based on that check, but the resource changes in the interim, leading to security bypasses. This vulnerability requires physical access to the device, which limits remote exploitation but raises concerns for environments where devices may be physically accessible to attackers, such as in offices, public spaces, or during transport.

For European organizations, this vulnerability poses a significant risk to data confidentiality and integrity, especially for entities relying on BitLocker for disk encryption on Windows 10 Version 1809 devices. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, where data protection is paramount, could face data breaches if attackers gain physical access to devices. The ability to bypass BitLocker encryption undermines trust in endpoint security and could lead to exposure of sensitive personal data protected under GDPR, resulting in regulatory penalties and reputational damage. Additionally, the availability impact is high, as attackers could potentially manipulate or corrupt data. The physical access requirement somewhat limits the threat scope but does not eliminate it, particularly in scenarios involving lost or stolen laptops, insider threats, or insufficient physical security controls. European organizations with a large deployment of Windows 10 Version 1809 may be disproportionately affected, especially if they have not upgraded to newer Windows versions or applied mitigations. The lack of known exploits in the wild currently reduces immediate risk, but the medium severity score and high impact on confidentiality and integrity warrant proactive measures.

1. Upgrade affected systems: European organizations should prioritize upgrading Windows 10 Version 1809 systems to the latest supported Windows 10 or Windows 11 versions where this vulnerability is addressed. 2. Enhance physical security: Implement strict physical access controls to prevent unauthorized individuals from accessing devices, including secure storage, access logging, and surveillance in sensitive areas. 3. Use multifactor authentication for device access: While BitLocker protects data at rest, combining it with strong authentication mechanisms (e.g., TPM with PIN or USB key) can add layers of protection. 4. Monitor device inventory and status: Maintain accurate inventories of devices running Windows 10 Version 1809 and monitor for lost or stolen devices to respond quickly to potential compromises. 5. Apply any available vendor mitigations: Monitor Microsoft advisories for patches or workarounds and apply them promptly once released. 6. Educate employees on device security: Train staff on the importance of physical security and reporting lost or stolen devices immediately. 7. Consider additional encryption or endpoint protection solutions that provide defense-in-depth beyond BitLocker. 8. For high-risk environments, consider disabling BitLocker on vulnerable versions until patched, if feasible, or restrict use of affected devices.