CVE-2025-21375 is a vulnerability identified in the Kernel Streaming WOW Thunk Service Driver component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The root cause is improper input validation (CWE-20), which can lead to an elevation of privilege condition. Specifically, the driver fails to adequately validate inputs, allowing a user with limited privileges (low-level user) to execute code or commands that escalate their privileges to a higher level, potentially SYSTEM or administrative rights. The vulnerability does not require user interaction (UI:N) and has a low attack complexity (AC:L), meaning exploitation is relatively straightforward once access to the system is obtained. The attack vector is local (AV:L), so the attacker must have some level of access to the affected machine. The impact is severe, affecting confidentiality, integrity, and availability (all rated high), which means an attacker could gain full control over the system, access sensitive data, modify system configurations, or disrupt services. No public exploits are known at this time, but the vulnerability is classified as high severity with a CVSS v3.1 score of 7.8. The vulnerability was published on February 11, 2025, and is currently unpatched as no patch links are provided. This makes it critical for organizations to monitor and prepare for patch deployment. The vulnerability is tagged with CWE-20 (Improper Input Validation) and also references CWE-122 (Heap-based Buffer Overflow), indicating potential memory corruption risks. Given the affected product is Windows 10 Version 1809, which is still in use in many enterprise environments, the threat is significant, especially for organizations that have not upgraded or patched their systems.

For European organizations, the impact of CVE-2025-21375 can be substantial. Elevation of privilege vulnerabilities allow attackers who have gained limited access—such as through phishing, malware, or insider threats—to escalate their privileges to administrative levels, enabling full control over affected systems. This can lead to unauthorized access to sensitive data, disruption of critical services, and the potential for lateral movement within corporate networks. Sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitive nature of their data and operations. The vulnerability affects Windows 10 Version 1809, which remains in use in many European enterprises, especially those with legacy systems or slower upgrade cycles. Exploitation could result in data breaches, operational downtime, and regulatory non-compliance under GDPR due to compromised confidentiality and integrity. The lack of known exploits currently reduces immediate risk, but the high severity and ease of exploitation mean that attackers may develop exploits rapidly once the vulnerability becomes widely known.

1. Immediate assessment of the Windows 10 Version 1809 deployment within the organization to identify vulnerable systems. 2. Apply official Microsoft patches as soon as they are released; monitor Microsoft security advisories closely. 3. Until patches are available, restrict local access to vulnerable systems by enforcing strict access controls and limiting user privileges. 4. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect and block suspicious privilege escalation attempts. 5. Conduct regular audits of user privileges and remove unnecessary administrative rights. 6. Employ network segmentation to limit lateral movement if a system is compromised. 7. Educate users about the risks of local access exploits and enforce strong authentication mechanisms. 8. Monitor system logs and security alerts for unusual activity indicative of privilege escalation attempts. 9. Plan and execute upgrades to supported and patched Windows versions to reduce exposure to legacy vulnerabilities. 10. Consider deploying host-based intrusion prevention systems (HIPS) that can intercept attempts to exploit kernel-level vulnerabilities.