CVE-2025-59505 is a double free vulnerability classified under CWE-415 found in the Windows Smart Card component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). A double free occurs when a program calls free() twice on the same memory address, leading to undefined behavior such as memory corruption, crashes, or arbitrary code execution. In this case, the vulnerability allows an authorized local attacker—someone with valid access to the system but without elevated privileges—to exploit the flaw to escalate their privileges. The attacker can leverage this to execute code with SYSTEM-level privileges, thereby gaining full control over the affected machine. The vulnerability does not require user interaction, making exploitation more straightforward once local access is obtained. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local, low attack complexity, low privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. No public exploits or patches are currently available, but the vulnerability is published and recognized by Microsoft. The flaw specifically affects Windows 10 Version 1809, a version that, while superseded by newer releases, remains in use in some environments, particularly those with legacy systems or strict compatibility requirements. The Windows Smart Card service is often used in enterprise environments for authentication, especially in government, finance, and critical infrastructure sectors, increasing the potential impact of this vulnerability.

For European organizations, the impact of CVE-2025-59505 can be significant, especially in sectors relying on Windows 10 Version 1809 and smart card authentication for secure access. Successful exploitation allows an attacker with local access to escalate privileges to SYSTEM level, potentially leading to full system compromise, data exfiltration, disruption of services, or lateral movement within networks. This threatens confidentiality, integrity, and availability of critical systems. Organizations in finance, government, healthcare, and critical infrastructure that use smart cards for authentication are particularly vulnerable. Legacy systems that have not been upgraded or patched remain at risk, and the lack of available patches increases exposure. The vulnerability could facilitate insider threats or attacks by adversaries who have gained limited access through phishing or physical access. Given the high impact and ease of exploitation once local access is obtained, the threat could lead to severe operational disruptions and regulatory compliance issues under GDPR and other European data protection laws.

1. Apply security updates and patches from Microsoft as soon as they become available for Windows 10 Version 1809. 2. If patching is not immediately possible, restrict local access to affected systems by enforcing strict access controls and monitoring local user activities. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. 4. Review and harden smart card authentication configurations to minimize attack surface, including disabling unnecessary services and enforcing least privilege principles. 5. Conduct regular audits of systems running Windows 10 Version 1809 to identify and remediate unpatched or vulnerable machines. 6. Educate users and administrators about the risks of local privilege escalation vulnerabilities and the importance of physical security. 7. Consider upgrading affected systems to supported Windows versions with ongoing security updates to reduce exposure to legacy vulnerabilities. 8. Implement network segmentation to limit the impact of potential compromises originating from exploited endpoints.