CVE-2025-59206 is a use-after-free vulnerability (CWE-416) found in the Windows Resilient File System (ReFS) Deduplication Service on Windows 11 Version 24H2 (build 10.0.26100.0). Use-after-free bugs occur when a program continues to use memory after it has been freed, potentially allowing attackers to execute arbitrary code or corrupt memory. In this case, the vulnerability exists in the deduplication service component of ReFS, which is responsible for optimizing storage by eliminating duplicate data blocks. The flaw allows an attacker with local access to elevate privileges, gaining higher system rights than intended. The CVSS v3.1 score is 7.4, reflecting high impact on confidentiality, integrity, and availability, but with high attack complexity and no privileges or user interaction required. The vulnerability was reserved on September 10, 2025, and published on October 14, 2025. No patches or known exploits are currently available, but the vulnerability poses a significant risk due to its potential to compromise system security. The deduplication service typically runs with elevated privileges, so exploiting this use-after-free bug could allow attackers to execute code in kernel or system context, leading to full system compromise.

If exploited, this vulnerability could allow attackers with local access to escalate privileges to SYSTEM or equivalent, bypassing security controls. This could lead to unauthorized access to sensitive data, installation of persistent malware, disruption of system services, or complete system takeover. Organizations relying on Windows 11 Version 24H2 with ReFS deduplication enabled—such as enterprises using ReFS for large-scale storage optimization—face risks of data breaches, operational disruption, and loss of data integrity. The high severity score indicates that confidentiality, integrity, and availability could all be severely impacted. Although exploitation requires local access and high complexity, insider threats or attackers who have already gained limited access could leverage this flaw to deepen their control. The absence of known exploits in the wild provides a window for proactive mitigation, but the lack of patches means organizations must be vigilant.

1. Monitor Microsoft security advisories closely and apply patches immediately once available. 2. Restrict local access to systems running Windows 11 Version 24H2 with ReFS deduplication enabled, limiting it to trusted administrators only. 3. Disable ReFS deduplication if not required, as this reduces the attack surface. 4. Employ endpoint detection and response (EDR) solutions to monitor for suspicious activities related to privilege escalation attempts. 5. Conduct regular audits of local user accounts and permissions to minimize the risk of unauthorized local access. 6. Use application whitelisting and privilege management to limit the ability of untrusted code to execute with elevated privileges. 7. Maintain robust backup and recovery procedures to mitigate potential data loss or corruption. 8. Educate system administrators about this vulnerability and the importance of applying updates promptly.