CVE-2025-59210 is a use-after-free vulnerability categorized under CWE-416 found in the Windows Resilient File System (ReFS) Deduplication Service on Windows 11 Version 25H2 (build 10.0.26200.0). The vulnerability arises due to improper handling of memory in the deduplication service, which is responsible for optimizing storage by eliminating duplicate data blocks. An attacker with local access and without any privileges or user interaction can exploit this flaw to elevate their privileges on the system. The CVSS v3.1 score of 7.4 reflects a high-severity issue with local attack vector, high attack complexity, no privileges required, and no user interaction needed. Successful exploitation could lead to full compromise of confidentiality, integrity, and availability of the system, potentially allowing arbitrary code execution or system crashes. Although no exploits are currently known in the wild and no patches have been published, the vulnerability's presence in a core Windows component used in enterprise environments makes it a critical concern. The deduplication service is typically enabled in environments that require efficient storage management, such as data centers and enterprise file servers. The vulnerability was reserved in early September 2025 and published in mid-October 2025, indicating recent discovery. The lack of patches necessitates immediate risk mitigation and monitoring until updates are available.

For European organizations, the impact of CVE-2025-59210 could be significant, especially for those relying on Windows 11 Version 25H2 with ReFS deduplication enabled in enterprise or critical infrastructure environments. Exploitation could allow local attackers to escalate privileges, potentially gaining administrative control over affected systems. This could lead to unauthorized access to sensitive data, disruption of services, and deployment of further malware or ransomware. Sectors such as finance, healthcare, government, and manufacturing, which often use deduplication for storage efficiency, are particularly at risk. The compromise of confidentiality, integrity, and availability could result in data breaches, operational downtime, and regulatory non-compliance under GDPR and other European data protection laws. The absence of known exploits currently reduces immediate risk, but the high severity and potential impact necessitate proactive defenses. Additionally, the requirement for local access limits remote exploitation but does not eliminate insider threats or attacks via compromised local accounts.

1. Restrict local access to systems running Windows 11 Version 25H2 with ReFS deduplication enabled, enforcing strict access controls and monitoring for unauthorized logins. 2. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior related to the deduplication service. 3. Disable ReFS deduplication on systems where it is not essential, reducing the attack surface. 4. Monitor system logs and security events for unusual activity involving the deduplication service or memory corruption indicators. 5. Prepare for rapid deployment of security patches from Microsoft once released by establishing a tested update process. 6. Conduct internal audits to identify systems running the affected Windows build and prioritize them for enhanced monitoring and access restrictions. 7. Educate IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of maintaining strict local user policies. 8. Use virtualization or sandboxing for high-risk environments to contain potential exploitation impacts.