CVE-2025-49675 is a high-severity use-after-free vulnerability identified in the Kernel Streaming WOW Thunk Service Driver component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises when the system improperly manages memory, specifically freeing memory that is still in use, which can lead to undefined behavior. An authorized local attacker with limited privileges can exploit this flaw to execute arbitrary code in kernel mode, thereby elevating their privileges to SYSTEM level. The vulnerability does not require user interaction and has a low attack complexity, but it does require local access and some privileges to initiate the exploit. The CVSS v3.1 score of 7.8 reflects the significant impact on confidentiality, integrity, and availability, as successful exploitation could allow an attacker to gain full control over the affected system. Although no known exploits are currently in the wild, the vulnerability's nature and impact make it a critical concern for organizations still running this Windows 10 version. The lack of available patches at the time of publication increases the urgency for mitigation and risk management.

For European organizations, this vulnerability poses a substantial risk, especially for those that continue to operate legacy systems running Windows 10 Version 1809. Exploitation could lead to unauthorized privilege escalation, enabling attackers to bypass security controls, access sensitive data, deploy malware, or disrupt critical services. This is particularly concerning for sectors with high-value targets such as finance, healthcare, government, and critical infrastructure, where compromise could result in significant operational, financial, and reputational damage. Given that the vulnerability requires local access, insider threats or attackers who have already gained limited footholds could leverage this flaw to deepen their control. The absence of known exploits currently provides a window for proactive defense, but the high severity and potential for kernel-level compromise necessitate immediate attention to prevent future exploitation.

European organizations should prioritize upgrading or patching affected systems as soon as Microsoft releases an official fix. In the interim, practical mitigation steps include: 1) Restricting local access to systems running Windows 10 Version 1809 by enforcing strict access controls and monitoring; 2) Implementing application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts; 3) Conducting thorough audits to identify and phase out legacy systems still running the vulnerable version; 4) Enhancing user privilege management by applying the principle of least privilege to limit the ability of users to execute code or access kernel components; 5) Monitoring system logs and kernel events for unusual activity related to the Kernel Streaming WOW Thunk Service Driver; 6) Educating IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of reporting suspicious behavior promptly.