CVE-2025-55687 is a race condition vulnerability classified under CWE-362, affecting the Windows Resilient File System (ReFS) in Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises from improper synchronization when multiple threads or processes concurrently access shared resources within ReFS, leading to a state where an attacker can manipulate the timing of operations to gain unauthorized elevated privileges locally. This vulnerability does not require prior authentication or user interaction, increasing its risk profile. The attacker must have local access but can exploit the race condition to bypass security controls, potentially gaining SYSTEM-level privileges. The vulnerability impacts confidentiality, integrity, and availability by allowing unauthorized access and control over the system. The CVSS v3.1 score is 7.4 (high), reflecting the complexity of exploitation (high attack complexity) and the local attack vector, but with no privileges or user interaction required. No public exploits are known yet, and no patches have been released at the time of publication. The vulnerability is critical for environments relying on ReFS for data integrity and resilience, such as enterprise storage and backup solutions. Attackers exploiting this flaw could execute arbitrary code with elevated privileges, compromise sensitive data, or disrupt system operations.

For European organizations, this vulnerability poses a significant threat, especially those using Windows 11 25H2 with ReFS in enterprise or critical infrastructure environments. Successful exploitation could lead to unauthorized privilege escalation, enabling attackers to bypass security controls, access sensitive data, and disrupt operations. This is particularly concerning for sectors like finance, healthcare, government, and energy, where data integrity and system availability are paramount. The local attack requirement limits remote exploitation but insider threats or compromised endpoints could leverage this vulnerability to escalate privileges and move laterally within networks. The potential impact includes data breaches, ransomware deployment with elevated privileges, and disruption of critical services. Given the high adoption rate of Windows 11 in Europe and the increasing use of ReFS in enterprise storage, the risk is substantial. Organizations may face regulatory and compliance consequences if exploited, especially under GDPR and other data protection laws.

Immediate mitigation involves applying official patches from Microsoft once they become available. Until then, organizations should restrict local access to systems running Windows 11 25H2 with ReFS, enforcing strict user privilege management and monitoring for unusual local activity indicative of exploitation attempts. Employ endpoint detection and response (EDR) tools to detect race condition exploitation patterns and privilege escalation behaviors. Disable or limit the use of ReFS where feasible, or isolate systems using ReFS to minimize exposure. Conduct regular audits of local accounts and remove unnecessary privileges. Implement application whitelisting and robust logging to detect unauthorized changes. Educate staff about the risks of local attacks and insider threats. Finally, maintain up-to-date backups and incident response plans tailored to privilege escalation scenarios.