CVE-2025-49661 is a high-severity vulnerability identified in Microsoft Windows 10 Version 1809, specifically in the Windows Ancillary Function Driver for WinSock. The vulnerability is classified under CWE-822, which pertains to untrusted pointer dereference. This type of flaw occurs when the software dereferences a pointer that can be controlled or influenced by an attacker, potentially leading to memory corruption or unauthorized code execution. In this case, an authorized local attacker can exploit this vulnerability to elevate their privileges on the affected system. The vulnerability requires local access with some level of privileges (PR:L) but does not require user interaction (UI:N). The attack vector is local (AV:L), meaning the attacker must have access to the system to exploit it. The vulnerability impacts confidentiality, integrity, and availability, all rated as high (C:H/I:H/A:H), indicating that successful exploitation could allow the attacker to gain full control over the system, access sensitive information, modify system data, or disrupt system operations. The CVSS score of 7.8 reflects the significant risk posed by this vulnerability. Although no known exploits are currently in the wild, the absence of a patch link suggests that remediation may not yet be widely available, increasing the urgency for affected organizations to monitor updates closely. The vulnerability affects Windows 10 Version 1809 (build 10.0.17763.0), which is an older version of Windows 10 but may still be in use in certain environments. The flaw lies in the Ancillary Function Driver for WinSock, a component responsible for network socket operations, which is critical for network communications on Windows systems. Exploiting this vulnerability could allow an attacker to execute code with elevated privileges, bypassing normal security controls and potentially leading to full system compromise.

For European organizations, the impact of CVE-2025-49661 could be substantial, especially for those still running Windows 10 Version 1809 in their IT environments. Privilege escalation vulnerabilities are particularly dangerous because they allow attackers who have gained limited access to a system to escalate their privileges and gain administrative control. This can lead to data breaches, disruption of business operations, and lateral movement within corporate networks. Given the high confidentiality, integrity, and availability impact, sensitive data such as personal information protected under GDPR could be exposed or manipulated, leading to regulatory penalties and reputational damage. Critical infrastructure operators, financial institutions, healthcare providers, and government agencies in Europe that rely on legacy Windows 10 systems may be at heightened risk. The lack of known exploits in the wild currently provides a window for proactive mitigation, but the potential for future exploitation means organizations must act swiftly to prevent compromise. Additionally, the local attack vector implies that insider threats or attackers who have already gained initial access through other means could leverage this vulnerability to deepen their foothold.

1. Immediate assessment of all Windows 10 systems to identify any running Version 1809 (build 10.0.17763.0) is critical. 2. Apply any available security patches or updates from Microsoft as soon as they are released; monitor Microsoft’s security advisories closely for patch availability. 3. If patching is not immediately possible, implement strict access controls to limit local user privileges and restrict access to systems running the affected version. 4. Employ endpoint detection and response (EDR) solutions to monitor for unusual local privilege escalation attempts or suspicious activity related to WinSock components. 5. Conduct regular audits of user accounts and permissions to minimize the number of users with local privileges that could exploit this vulnerability. 6. Use application whitelisting and restrict execution of unauthorized code to reduce the risk of exploitation. 7. Educate IT staff and users about the risks of local privilege escalation and the importance of reporting suspicious behavior. 8. Consider upgrading affected systems to a more recent, supported version of Windows 10 or Windows 11 to benefit from improved security features and ongoing support.