CVE-2025-53137 is a high-severity use-after-free vulnerability identified in the Windows Ancillary Function Driver for WinSock component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises from improper handling of memory, where the system attempts to use memory after it has been freed, leading to undefined behavior. Specifically, an authorized local attacker with limited privileges (local privilege level) can exploit this flaw to elevate their privileges on the affected system. The vulnerability does not require user interaction but does require local access and a higher attack complexity, indicating some conditions must be met for successful exploitation. The CVSS v3.1 base score is 7.0, reflecting high impact on confidentiality, integrity, and availability. The vulnerability impacts confidentiality by potentially allowing unauthorized access to sensitive data, integrity by enabling modification of system state or code execution with elevated privileges, and availability by possibly causing system instability or crashes. No known exploits are currently reported in the wild, and no patches have been linked yet, which suggests organizations should prioritize mitigation and monitoring. The vulnerability is categorized under CWE-416 (Use After Free), a common memory corruption issue that can lead to arbitrary code execution or system compromise if exploited successfully.

For European organizations, this vulnerability poses a significant risk, especially for those running legacy Windows 10 Version 1809 systems in critical infrastructure, government, finance, healthcare, or industrial environments. Successful exploitation could allow attackers to escalate privileges locally, bypassing security controls and gaining administrative access. This could lead to unauthorized data access, deployment of malware or ransomware, disruption of services, or further lateral movement within networks. Given that Windows 10 Version 1809 is an older release, many organizations may still have it deployed in legacy systems or specialized environments, increasing exposure. The lack of known exploits in the wild provides a window for proactive defense, but the high severity and potential for privilege escalation make timely mitigation essential to prevent targeted attacks or insider threats. Additionally, the vulnerability could be leveraged in multi-stage attacks where initial access is limited, but privilege escalation is needed to achieve full control.

European organizations should immediately identify and inventory all systems running Windows 10 Version 1809 (build 10.0.17763.0) to assess exposure. Since no official patches are linked yet, organizations should monitor Microsoft security advisories closely for updates and apply patches promptly once available. In the interim, applying strict access controls to limit local user privileges can reduce the attack surface. Employing application whitelisting and endpoint detection and response (EDR) solutions can help detect anomalous behavior indicative of exploitation attempts. Network segmentation and limiting administrative access to critical systems will further contain potential breaches. Regularly auditing and hardening WinSock configurations and related network components may reduce risk. Additionally, organizations should educate users about the risks of local privilege escalation and enforce policies that minimize unnecessary local access. Finally, consider upgrading affected systems to supported Windows versions with active security updates to eliminate exposure to this vulnerability.