CVE-2025-55687 is a race condition vulnerability classified under CWE-362, found in the Windows Resilient File System (ReFS) component of Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises due to improper synchronization when multiple concurrent processes access shared resources within ReFS, leading to a race condition. This condition can be exploited by an unauthorized local attacker to elevate privileges on the affected system. The vulnerability impacts the confidentiality, integrity, and availability of the system by potentially allowing attackers to execute code with elevated privileges, modify or corrupt data, or disrupt system operations. The CVSS v3.1 base score is 7.4, indicating high severity, with an attack vector limited to local access (AV:L), high attack complexity (AC:H), no privileges required (PR:N), and no user interaction (UI:N). The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). No known exploits are currently reported in the wild, and no patches have been publicly released yet. The vulnerability was reserved in August 2025 and published in October 2025. Given the nature of ReFS usage primarily in enterprise environments for data integrity and resilience, this vulnerability poses a significant risk to organizations relying on Windows 11 25H2 with ReFS volumes.

For European organizations, this vulnerability presents a significant risk especially to enterprises and public sector entities that utilize Windows 11 Version 25H2 with ReFS for critical data storage and resilience. Successful exploitation could lead to unauthorized privilege escalation, enabling attackers to gain administrative control, potentially leading to data breaches, system manipulation, or denial of service. This could compromise sensitive personal data protected under GDPR, disrupt business operations, and damage organizational reputation. Sectors such as finance, healthcare, government, and critical infrastructure are particularly vulnerable due to their reliance on secure and resilient file systems. The local access requirement limits remote exploitation but insider threats or attackers with initial footholds could leverage this vulnerability to escalate privileges and move laterally within networks. The absence of known exploits currently provides a window for proactive mitigation but also underscores the need for vigilance as exploit development could follow.

Organizations should prioritize deploying official patches from Microsoft once available to address this vulnerability. Until patches are released, implement strict local access controls to limit user permissions and reduce the risk of unauthorized local access. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for unusual privilege escalation attempts or suspicious process behavior related to ReFS operations. Regularly audit systems for unauthorized changes and ensure that ReFS volumes are used only where necessary, considering alternative file systems if feasible. Additionally, enforce strong internal network segmentation to limit lateral movement opportunities for attackers who gain local access. Educate IT staff and users about the risks of local privilege escalation vulnerabilities and maintain up-to-date incident response plans to quickly address potential exploitation attempts.