CVE-2025-59242 is a heap-based buffer overflow vulnerability identified in the Windows Ancillary Function Driver for WinSock component on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises from improper handling of memory buffers in the driver, leading to a condition where an attacker with authorized local access can overwrite heap memory. The overflow can corrupt adjacent memory structures, allowing the attacker to execute arbitrary code or escalate privileges to SYSTEM level. The flaw does not require user interaction and has a low attack complexity, but it does require the attacker to have some level of local privileges (PR:L). The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation could allow an attacker to gain full control over the affected system. Although no public exploits are currently known, the vulnerability is rated with a CVSS v3.1 base score of 7.8, indicating high severity. The vulnerability was reserved in September 2025 and published in October 2025. No patches are linked yet, suggesting that organizations should monitor for updates from Microsoft. The affected product is a legacy Windows 10 version, which remains in use in certain enterprise environments. The Ancillary Function Driver for WinSock is a core networking component, so exploitation could facilitate lateral movement or persistence within a network.

For European organizations, this vulnerability poses a significant risk especially to those still operating Windows 10 Version 1809 in production environments. Successful exploitation allows local attackers to escalate privileges, potentially leading to full system compromise. This can result in unauthorized access to sensitive data, disruption of critical services, and the ability to deploy further malware or ransomware. Given the networking nature of the vulnerable component, attackers could leverage this to move laterally within corporate networks, increasing the scope of impact. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitivity of their data and services. The lack of known exploits currently reduces immediate risk, but the high severity and ease of exploitation mean that threat actors could develop exploits rapidly once patches are released or if reverse engineering occurs. Legacy systems that cannot be upgraded easily are especially vulnerable, increasing the attack surface in European enterprises with long hardware/software lifecycles.

1. Prioritize patch management: Monitor Microsoft security advisories closely and apply patches immediately once released for Windows 10 Version 1809. 2. Restrict local access: Limit administrative and local user privileges to trusted personnel only, reducing the pool of potential attackers who can exploit this vulnerability. 3. Implement application whitelisting and endpoint protection to detect and block suspicious activities that may indicate exploitation attempts. 4. Employ network segmentation to contain potential lateral movement if a system is compromised. 5. Conduct regular vulnerability scanning and penetration testing focusing on legacy systems to identify and remediate exposures. 6. Consider upgrading affected systems to supported Windows versions with ongoing security updates to reduce exposure to legacy vulnerabilities. 7. Use monitoring and logging to detect unusual privilege escalation attempts or anomalous behavior on endpoints running Windows 10 1809. 8. Educate IT staff about the risks of legacy OS usage and the importance of timely patching and access control.