CVE-2025-59277 is a vulnerability categorized under CWE-1287, indicating improper validation of the specified type of input within Windows Authentication Methods on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This flaw allows an attacker who already has some level of local access and privileges to escalate their privileges further, potentially gaining administrative rights. The vulnerability arises because the system does not correctly validate the type of input it receives during authentication processes, which can be manipulated by an authorized local user to bypass security controls. The CVSS v3.1 base score is 7.8, reflecting high severity due to the impact on confidentiality, integrity, and availability, combined with relatively low attack complexity and no requirement for user interaction. Although no public exploits are known at this time, the vulnerability poses a significant risk to environments where Windows 10 Version 1809 is still operational, especially since this version is out of mainstream support and may not receive timely patches. The lack of available patches necessitates immediate mitigation through compensating controls. The vulnerability's exploitation scope is local, requiring the attacker to have some privileges already, but once exploited, it can lead to full system compromise, enabling unauthorized access to sensitive data, modification of system configurations, and disruption of services.

For European organizations, this vulnerability presents a critical risk particularly to sectors that continue to operate legacy Windows 10 Version 1809 systems, such as manufacturing, healthcare, government, and critical infrastructure. Successful exploitation can lead to unauthorized privilege escalation, allowing attackers to gain administrative control, which could result in data breaches, sabotage, or ransomware deployment. The impact on confidentiality is high as attackers could access sensitive information; integrity is compromised as system configurations and security controls can be altered; availability is at risk if attackers disrupt services or deploy destructive payloads. Given the local access requirement, insider threats or attackers who have already compromised lower-privileged accounts pose the greatest risk. The absence of known exploits in the wild currently reduces immediate threat levels but does not diminish the urgency for mitigation, especially in environments with high-value targets or regulatory compliance requirements such as GDPR.

1. Immediately audit and restrict local user privileges to the minimum necessary, preventing unnecessary local access that could be leveraged for privilege escalation. 2. Implement strict access control policies and use application whitelisting to limit execution of unauthorized code. 3. Monitor event logs and authentication attempts for unusual privilege escalation activities or anomalies in authentication methods. 4. Employ endpoint detection and response (EDR) tools capable of detecting suspicious local privilege escalation behaviors. 5. Plan and prioritize upgrading affected systems from Windows 10 Version 1809 to a supported and patched Windows version as soon as possible. 6. Until patches are available, consider isolating legacy systems or restricting network access to reduce exposure. 7. Educate IT staff and users about the risks of local privilege escalation and enforce strong local account management practices. 8. Regularly review and update security policies to incorporate controls against exploitation of authentication-related vulnerabilities.