CVE-2025-26640 is a high-severity use-after-free vulnerability (CWE-416) found in the Windows Digital Media component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability allows an authorized local attacker to elevate privileges on the affected system. A use-after-free flaw occurs when a program continues to use a pointer after the memory it points to has been freed, leading to undefined behavior such as memory corruption, crashes, or execution of arbitrary code. In this case, exploitation could allow an attacker with limited privileges (local user with some level of access) to execute code with higher privileges, potentially SYSTEM level, thereby gaining full control over the affected machine. The vulnerability does not require user interaction but does require local access and a higher attack complexity due to the need for high attack complexity (AC:H). The CVSS 3.1 base score is 7.0, reflecting high impact on confidentiality, integrity, and availability (all rated high), but limited by the requirement for local access and privileges. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may currently rely on workarounds or system hardening. The vulnerability was reserved in February 2025 and published in April 2025, indicating recent discovery and disclosure. The affected Windows 10 Version 1809 is an older release, but still in use in some environments, especially in legacy or specialized systems. The vulnerability’s exploitation could allow attackers to bypass security controls and escalate privileges, potentially leading to full system compromise, data theft, or disruption of services.

For European organizations, this vulnerability poses a significant risk especially to those still running legacy Windows 10 Version 1809 systems, which may be present in industrial, governmental, or enterprise environments where upgrading is delayed due to compatibility or operational constraints. Successful exploitation could lead to unauthorized privilege escalation, enabling attackers to deploy malware, steal sensitive data, or disrupt critical services. This is particularly concerning for sectors with high-value targets such as finance, healthcare, energy, and government institutions. The confidentiality, integrity, and availability of systems could be severely impacted, potentially leading to data breaches, operational downtime, and regulatory non-compliance under GDPR and other data protection laws. The requirement for local access limits remote exploitation but insider threats or attackers gaining initial footholds through other means could leverage this vulnerability to deepen their control. The absence of known exploits in the wild reduces immediate risk but also means organizations should proactively address the vulnerability before exploitation occurs.

Given the lack of an official patch at this time, European organizations should implement specific mitigations beyond generic advice: 1) Identify and inventory all systems running Windows 10 Version 1809 to assess exposure. 2) Restrict local access to critical systems by enforcing strict access controls, including the use of least privilege principles and multi-factor authentication for local logins. 3) Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious activities indicative of privilege escalation attempts. 4) Disable or restrict use of the Windows Digital Media component where feasible, or apply system hardening measures to reduce attack surface. 5) Monitor system logs and security alerts for unusual behavior that could indicate exploitation attempts. 6) Plan and prioritize upgrading affected systems to supported Windows versions with active security updates. 7) Educate users and administrators about the risks of local privilege escalation vulnerabilities and the importance of timely patching once available. 8) Implement network segmentation to limit lateral movement if a local compromise occurs.