CVE-2025-62456 is a heap-based buffer overflow vulnerability identified in the Windows Resilient File System (ReFS) component of Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises from improper handling of memory buffers within ReFS, which is a file system designed to improve data integrity and resilience against corruption. An attacker with authorized network access and low privileges can exploit this vulnerability to execute arbitrary code remotely, potentially gaining control over the affected system. The vulnerability does not require user interaction, increasing its risk profile. The CVSS v3.1 base score is 8.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction required. Although no public exploits have been reported yet, the vulnerability's characteristics suggest it could be weaponized for remote code execution attacks, ransomware deployment, or lateral movement within networks. The vulnerability was reserved in mid-October 2025 and published in early December 2025, with no patches currently available, indicating a window of exposure. Organizations using Windows 11 with ReFS, particularly in enterprise environments where ReFS is used for large-scale storage or backup solutions, are at risk. The vulnerability's network attack vector and requirement for only low privileges make it a significant threat to enterprise security postures.

For European organizations, this vulnerability poses a substantial risk due to the widespread adoption of Windows 11 in enterprise and government sectors. The ability to execute arbitrary code remotely can lead to full system compromise, data breaches, ransomware infections, and disruption of critical services. Organizations relying on ReFS for data integrity and storage resilience may face data corruption or loss if exploited. The vulnerability could facilitate lateral movement within networks, enabling attackers to escalate privileges and access sensitive information. The lack of available patches increases the urgency for interim mitigations. Critical infrastructure, financial institutions, healthcare providers, and government agencies in Europe could be targeted due to their reliance on Windows 11 and the strategic value of their data. The potential for widespread impact is heightened by the network-based attack vector and the absence of required user interaction, making automated exploitation feasible.

1. Immediately restrict network access to systems running Windows 11 Version 25H2 with ReFS enabled, especially from untrusted networks. 2. Implement strict firewall rules to limit SMB and other file system-related network protocols to trusted hosts only. 3. Monitor network traffic and system logs for unusual activity indicative of exploitation attempts, such as unexpected ReFS-related errors or anomalous process behavior. 4. Employ endpoint detection and response (EDR) solutions with updated signatures and heuristics to detect exploitation attempts targeting ReFS. 5. Disable or avoid using ReFS on systems where it is not essential until a patch is released. 6. Prepare for rapid deployment of official patches from Microsoft once available by maintaining an up-to-date asset inventory and patch management process. 7. Conduct user and administrator awareness training to recognize signs of compromise related to this vulnerability. 8. Segment critical systems and implement network segmentation to contain potential breaches. 9. Regularly back up critical data using secure, offline methods to mitigate the impact of potential ransomware attacks exploiting this vulnerability.