CVE-2025-30400 is a high-severity use-after-free vulnerability (CWE-416) found in the Desktop Window Manager (DWM) component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability allows an authorized local attacker with limited privileges (PR:L) to execute a use-after-free condition, which can lead to arbitrary code execution within the context of the DWM process. Exploiting this flaw enables the attacker to elevate their privileges to SYSTEM level, thereby gaining full control over the affected system. The vulnerability does not require user interaction (UI:N) and has a low attack complexity (AC:L), meaning exploitation is feasible without specialized conditions. The scope is unchanged (S:U), indicating the impact is confined to the vulnerable component. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits are currently reported in the wild, the presence of a functional exploit is plausible given the nature of use-after-free vulnerabilities. The lack of available patches at the time of publication increases the risk for unpatched systems. This vulnerability is particularly critical because it allows privilege escalation from a local user context without requiring user interaction, making it a prime candidate for post-compromise lateral movement or persistence mechanisms in targeted attacks.

For European organizations, the impact of CVE-2025-30400 is significant. Many enterprises and public sector entities still operate legacy Windows 10 Version 1809 systems due to compatibility or operational constraints. Successful exploitation could allow attackers to bypass local security controls, escalate privileges, and deploy malware or ransomware with SYSTEM-level permissions. This can lead to data breaches, disruption of critical services, and compromise of sensitive information. The high impact on confidentiality, integrity, and availability means that critical infrastructure, government agencies, healthcare providers, and financial institutions are at heightened risk. Additionally, the vulnerability could be leveraged in multi-stage attacks where initial access is gained through lower-privileged accounts, enabling attackers to gain full control over endpoints. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the ease of exploitation and high impact necessitate urgent attention to prevent potential exploitation in European environments.

Given the absence of official patches at the time of this report, European organizations should implement the following specific mitigations: 1) Restrict local user permissions rigorously to minimize the number of accounts with local access, especially limiting administrative privileges. 2) Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious behavior indicative of exploitation attempts targeting DWM or related processes. 3) Use Windows Defender Exploit Guard or similar exploit mitigation technologies to harden the system against use-after-free and memory corruption vulnerabilities. 4) Isolate legacy Windows 10 Version 1809 systems from critical network segments and sensitive data stores to reduce attack surface and lateral movement opportunities. 5) Conduct thorough asset inventories to identify all systems running the affected version and prioritize their upgrade or replacement. 6) Monitor security advisories from Microsoft closely for the release of official patches and apply them immediately upon availability. 7) Educate IT staff and users about the risks of local privilege escalation vulnerabilities and enforce strict endpoint security policies. These targeted actions go beyond generic advice by focusing on minimizing local attack vectors, enhancing detection capabilities, and isolating vulnerable systems within the network.