CVE-2025-59206 is a use-after-free vulnerability classified under CWE-416 found in the Windows Resilient File System (ReFS) Deduplication Service on Windows 11 Version 25H2 (build 10.0.26200.0). Use-after-free vulnerabilities occur when software continues to use memory after it has been freed, potentially leading to arbitrary code execution or privilege escalation. In this case, the flaw allows an attacker to elevate privileges on the affected system. The vulnerability requires local access (attack vector: local), has high attack complexity, and does not require user interaction or prior authentication. The impact is critical, affecting confidentiality, integrity, and availability, as an attacker could gain elevated privileges and potentially full control over the system. The vulnerability is currently published with no known exploits in the wild and no patches released yet. The ReFS Deduplication Service is a specialized feature used primarily in environments that utilize ReFS for storage efficiency. The vulnerability’s CVSS v3.1 score is 7.4, indicating high severity, with the vector string AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H, meaning local attack, high complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality, integrity, and availability. This vulnerability poses a significant risk to systems running the specified Windows 11 version, especially in enterprise and critical infrastructure environments where ReFS is deployed.

For European organizations, this vulnerability could lead to unauthorized privilege escalation on Windows 11 systems running the affected version with ReFS deduplication enabled. This could result in attackers gaining administrative control, leading to data breaches, disruption of services, or deployment of ransomware and other malware. Critical sectors such as finance, healthcare, government, and energy that rely on Windows 11 and ReFS for storage efficiency could face operational disruptions and data integrity issues. The requirement for local access limits remote exploitation but insider threats or attackers with initial foothold could leverage this vulnerability to escalate privileges. The absence of known exploits currently provides a window for proactive mitigation, but the high impact necessitates urgent attention. The vulnerability could also affect cloud service providers and managed service providers operating Windows 11 25H2 environments, potentially impacting multiple European clients.

1. Restrict local access to systems running Windows 11 Version 25H2 with ReFS deduplication enabled by enforcing strict physical and network access controls. 2. Monitor logs and system behavior for unusual activity related to the ReFS Deduplication Service, including unexpected process executions or privilege escalations. 3. Employ endpoint detection and response (EDR) solutions capable of detecting use-after-free exploitation techniques and privilege escalation attempts. 4. Disable ReFS deduplication if not required, as a temporary workaround until a patch is available. 5. Maintain up-to-date backups and ensure recovery plans are tested to mitigate potential ransomware or data corruption attacks stemming from exploitation. 6. Apply the official security patch from Microsoft immediately upon release. 7. Educate IT staff and users about the risks of local privilege escalation and enforce least privilege principles to limit potential attack vectors. 8. Conduct regular vulnerability assessments and penetration testing focusing on local privilege escalation vectors in Windows environments.