CVE-2025-59210 is a use-after-free vulnerability classified under CWE-416, affecting the Windows Resilient File System (ReFS) Deduplication Service in Windows 11 Version 25H2 (build 10.0.26200.0). Use-after-free vulnerabilities occur when a program continues to use memory after it has been freed, potentially allowing attackers to execute arbitrary code or escalate privileges. In this case, the flaw enables an elevation of privilege, meaning an attacker with local access can gain higher system privileges than intended. The vulnerability has a CVSS 3.1 base score of 7.4, indicating high severity, with the vector AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. This means the attack requires local access (AV:L), high attack complexity (AC:H), no privileges or user interaction (PR:N/UI:N), and impacts confidentiality, integrity, and availability severely (all high). The vulnerability is currently published but lacks known exploits in the wild and no patches have been released yet. The ReFS Deduplication Service is used to optimize storage by eliminating duplicate data blocks, often employed in enterprise environments. Exploitation could allow attackers to bypass security controls and gain full control over affected systems. The lack of user interaction and privileges required makes it a significant threat if local access is obtained, such as through other vulnerabilities or insider threats. The vulnerability was reserved in early September 2025 and published in mid-October 2025, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a significant risk especially to enterprises and government agencies using Windows 11 Version 25H2 with ReFS deduplication enabled. The potential impact includes unauthorized access to sensitive data, disruption of critical services, and full system compromise. Confidentiality, integrity, and availability of data stored on ReFS volumes could be severely affected. Organizations in sectors such as finance, healthcare, and critical infrastructure that rely on Windows 11 and ReFS for data storage and deduplication are particularly vulnerable. The requirement for local access limits remote exploitation but does not eliminate risk, as attackers could leverage other vulnerabilities or insider threats to gain initial foothold. The absence of patches means organizations must be vigilant and implement compensating controls to prevent exploitation. The high attack complexity reduces the likelihood of widespread exploitation but targeted attacks against high-value targets remain a concern.

1. Restrict local access to systems running Windows 11 Version 25H2 with ReFS deduplication enabled by enforcing strict access controls and monitoring user activity. 2. Implement robust endpoint detection and response (EDR) solutions to identify suspicious behavior indicative of exploitation attempts, such as unusual memory usage or process anomalies related to the ReFS service. 3. Limit the use of ReFS deduplication in environments where it is not essential, or consider disabling the deduplication service temporarily until patches are available. 4. Conduct regular audits of local accounts and privileges to minimize the risk of privilege escalation through compromised accounts. 5. Prepare for rapid deployment of official patches once released by Microsoft by maintaining an up-to-date asset inventory and patch management process. 6. Educate IT and security teams about the vulnerability details and encourage vigilance for any signs of exploitation. 7. Employ network segmentation to isolate critical systems and reduce the risk of lateral movement if local access is gained. 8. Monitor threat intelligence feeds for any emerging exploit code or attack campaigns targeting this vulnerability.