CVE-2025-59242 is a heap-based buffer overflow 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 due to improper handling of memory buffers on the heap, which can be exploited by an authorized local attacker to execute arbitrary code with elevated privileges. Specifically, the flaw allows the attacker to overwrite critical memory structures, potentially leading to full system compromise by escalating their privileges from a lower-level user to SYSTEM or equivalent. The vulnerability does not require user interaction and has a low attack complexity, but it does require local access and some privileges (PR:L). The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability. Although no public exploits have been reported yet, the nature of the vulnerability and its location in a core networking driver make it a significant risk. The affected Windows 10 Version 1809 is an older release, but still in use in various enterprise environments, especially those with legacy systems or delayed upgrade cycles. The vulnerability was reserved on 2025-09-11 and published on 2025-10-14, with no patch links currently available, indicating that remediation may still be pending or in progress.

For European organizations, this vulnerability poses a serious risk of local privilege escalation, which can be leveraged by insiders or attackers who have gained limited access to a system. Successful exploitation could allow attackers to bypass security controls, install persistent malware, access sensitive data, or disrupt system availability. Organizations relying on Windows 10 Version 1809, particularly in sectors with strict regulatory requirements such as finance, healthcare, and government, may face compliance and operational risks. The vulnerability's exploitation could facilitate lateral movement within networks, increasing the potential scope of compromise. Given the absence of known exploits in the wild, the immediate risk is moderate, but the potential impact is high if exploited. Legacy systems that have not been upgraded or patched are particularly vulnerable, which is a common scenario in some European enterprises with long hardware refresh cycles or strict change management policies.

1. Prioritize upgrading affected systems from Windows 10 Version 1809 to a supported and patched Windows version to eliminate exposure. 2. Apply security patches from Microsoft immediately once they become available for this vulnerability. 3. Restrict local access to critical systems by enforcing strict user account controls and limiting administrative privileges. 4. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of privilege escalation attempts. 5. Conduct regular audits of user privileges and monitor logs for suspicious local activity, especially related to WinSock or networking driver components. 6. Use network segmentation to limit the impact of compromised hosts and reduce the attack surface. 7. Educate IT staff and users about the risks of local privilege escalation and the importance of maintaining updated systems. 8. Employ vulnerability scanning tools to identify systems still running the vulnerable Windows 10 version and prioritize remediation accordingly.