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). The vulnerability arises due to improper handling of memory in the deduplication service, which can lead to the use of freed memory, potentially allowing an attacker to execute arbitrary code or escalate privileges. The flaw specifically enables elevation of privilege, meaning an attacker with local access but no prior privileges can exploit the bug to gain higher-level permissions on the system. The CVSS v3.1 score of 7.4 indicates a high severity, with an attack vector limited to local (AV:L), requiring high attack complexity (AC:H), no privileges (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 published as of the vulnerability disclosure date (October 14, 2025). The vulnerability affects Windows 11 25H2, specifically version 10.0.26200.0, and targets the ReFS deduplication service, a component used to optimize storage by eliminating duplicate data. Given the critical nature of file system services, exploitation could allow attackers to compromise system stability and security, potentially leading to full system control. The vulnerability was reserved on September 10, 2025, and published shortly after, indicating a recent discovery. Organizations relying on ReFS for storage deduplication, particularly in environments where local access cannot be tightly controlled, are at risk. The lack of patches necessitates immediate mitigation strategies to reduce exposure until an official fix is released.

For European organizations, this vulnerability poses a significant risk, especially those using Windows 11 Version 25H2 with ReFS deduplication enabled. The ability to elevate privileges locally without user interaction means that any insider threat, compromised local account, or malware with local presence could exploit this flaw to gain full control over affected systems. This could lead to unauthorized access to sensitive data, disruption of critical services, and potential spread of malware or ransomware. Sectors such as finance, healthcare, government, and critical infrastructure, which often use advanced storage solutions like ReFS for data integrity and efficiency, are particularly vulnerable. The high impact on confidentiality, integrity, and availability could result in severe operational disruptions and data breaches, with regulatory and reputational consequences under European data protection laws like GDPR. Additionally, the absence of known exploits currently provides a window for proactive defense, but also means organizations must act swiftly to prevent future exploitation once public exploit code or malware emerge.

1. Restrict local access to systems running Windows 11 Version 25H2 with ReFS deduplication enabled, limiting user permissions and enforcing strict access controls. 2. Monitor system logs and security events for unusual activity related to the ReFS deduplication service or privilege escalation attempts. 3. Disable or limit the use of ReFS deduplication where feasible, especially on systems exposed to multiple users or less trusted environments. 4. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect and block suspicious behaviors indicative of exploitation attempts. 5. Prepare for rapid deployment of official patches from Microsoft once released by establishing a tested update process and prioritizing affected systems. 6. Conduct internal audits to identify all systems running the vulnerable Windows 11 build and assess their exposure based on user access and service usage. 7. Educate IT and security teams about the vulnerability specifics to enhance detection and response capabilities. 8. Employ network segmentation to isolate critical systems and reduce the risk of lateral movement following exploitation.