CVE-2025-30400 is a high-severity use-after-free vulnerability identified in the Desktop Window Manager (DWM) component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability is classified under CWE-416, which refers to use-after-free errors where a program continues to use memory after it has been freed, potentially leading to arbitrary code execution or privilege escalation. In this case, the flaw allows an authorized local attacker with limited privileges (PR:L) to exploit the vulnerability without requiring user interaction (UI:N) to elevate their privileges to a higher level on the affected system. The attack vector is local (AV:L), meaning the attacker must have some form of access to the system, such as a standard user account. The vulnerability impacts confidentiality, integrity, and availability, all rated as high, indicating that successful exploitation could lead to full system compromise. The vulnerability has an exploitability factor marked as functional (E:F) and is officially published and recognized by Microsoft and CISA, although no known exploits are currently reported in the wild. The lack of a patch link suggests that a fix may be pending or not yet publicly released at the time of this report. The vulnerability's scope is unchanged (S:U), meaning the impact is confined to the vulnerable component without affecting other system components directly. Given the nature of DWM, which manages graphical user interface rendering, exploitation could allow attackers to execute arbitrary code with elevated privileges, potentially leading to full system control.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and government agencies that continue to operate legacy systems running Windows 10 Version 1809. Successful exploitation could allow attackers to escalate privileges from a standard user to SYSTEM or administrator level, enabling them to bypass security controls, install persistent malware, exfiltrate sensitive data, or disrupt critical services. This is particularly concerning for sectors with strict data protection requirements such as finance, healthcare, and public administration. The local attack vector means that attackers would need initial access, which could be gained through phishing, insider threats, or other means. Once inside, the vulnerability could facilitate lateral movement and privilege escalation within networks. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as proof-of-concept exploits could emerge rapidly. The high CVSS score (7.8) reflects the severity and potential impact on confidentiality, integrity, and availability, emphasizing the need for prompt mitigation.

European organizations should prioritize the following mitigation steps: 1) Identify and inventory all systems running Windows 10 Version 1809, focusing on those with the specific build 10.0.17763.0. 2) Apply any available security updates or patches from Microsoft as soon as they are released; monitor official Microsoft security advisories closely. 3) Implement strict access controls to limit local user privileges, minimizing the number of users with local accounts that could exploit this vulnerability. 4) Employ application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. 5) Use network segmentation to restrict lateral movement opportunities if an attacker gains initial access. 6) Conduct user awareness training to reduce the risk of initial compromise vectors such as phishing. 7) Consider upgrading affected systems to a supported and fully patched Windows version to eliminate exposure to legacy vulnerabilities. 8) Monitor system logs and security alerts for signs of privilege escalation attempts related to DWM or unusual process behavior. These targeted actions go beyond generic patching advice by emphasizing proactive detection, access restriction, and system modernization.