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). The vulnerability arises from improper handling of memory buffers in the WinSock driver, which is responsible for network socket operations. An authorized local attacker can exploit this flaw by triggering a buffer overflow condition, leading to arbitrary code execution with elevated privileges. This allows the attacker to escalate their privileges from a limited user context to SYSTEM-level access, compromising the confidentiality, integrity, and availability of the affected system. The vulnerability has a CVSS v3.1 base score of 7.8, indicating high severity, with attack vector local (AV:L), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), and unchanged scope (S:U). Although no public exploits are known at this time, the vulnerability's characteristics suggest it could be weaponized relatively easily by attackers with local access. The flaw specifically affects Windows 10 Version 1809, a version that, while superseded by newer releases, remains in use in some enterprise and industrial environments. The lack of available patches at the time of publication increases the urgency for organizations to implement compensating controls and prepare for imminent remediation. This vulnerability is categorized under CWE-122 (Heap-based Buffer Overflow), a common and dangerous class of memory corruption bugs that often lead to privilege escalation and system compromise.

For European organizations, the impact of CVE-2025-59242 can be significant, especially for those still running Windows 10 Version 1809 in production environments. Successful exploitation allows attackers with local access to gain SYSTEM-level privileges, potentially leading to full control over affected machines. This can result in unauthorized access to sensitive data, disruption of critical services, and the ability to deploy further malware or ransomware. Sectors such as manufacturing, healthcare, government, and finance, which may have legacy systems or slower upgrade cycles, are particularly vulnerable. The vulnerability's exploitation could facilitate lateral movement within networks, undermining network segmentation and increasing the risk of widespread compromise. Additionally, the absence of known exploits currently does not preclude rapid development and deployment of exploit code, especially given the low complexity and local attack vector. The impact on confidentiality, integrity, and availability is high, making timely mitigation essential to prevent potential breaches and operational disruptions.

1. Prioritize upgrading affected systems from Windows 10 Version 1809 to a supported, patched version of Windows 10 or later, as Microsoft typically provides security fixes in newer releases. 2. Until patches are available, restrict local access to systems running the vulnerable version by enforcing strict access controls, including limiting administrative privileges and using endpoint protection solutions to monitor suspicious activities. 3. Implement application whitelisting and behavior-based detection to identify attempts to exploit the WinSock driver. 4. Employ network segmentation to isolate legacy systems and reduce the risk of lateral movement if an exploit occurs. 5. Regularly audit and monitor logs for unusual privilege escalation attempts or anomalous network socket operations. 6. Educate users and administrators about the risks of local privilege escalation vulnerabilities and the importance of applying updates promptly. 7. Prepare incident response plans that include scenarios involving local privilege escalation to ensure rapid containment and remediation. 8. Use virtualization or sandboxing for legacy applications that require Windows 10 Version 1809 to limit exposure.