CVE-2025-55696 is a vulnerability classified under CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition) affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw exists in the NtQueryInformationToken function, which is part of the Windows kernel's native API used to query security token information. The vulnerability allows a local attacker with authorized access to exploit a race condition between the time a security check is performed and the time the resource is used, enabling them to elevate their privileges. This race condition can be triggered because the function does not properly synchronize access to token information, allowing an attacker to manipulate the token state during the check and use phases. Exploiting this flaw can lead to full system compromise by granting SYSTEM-level privileges, thereby compromising confidentiality, integrity, and availability of the affected system. The CVSS v3.1 base score is 7.8, reflecting high severity due to local attack vector, low complexity, and no user interaction required. Although no public exploits are currently known, the vulnerability is critical for environments where Windows 10 Version 1809 remains in use, especially since this version is no longer the latest and may lack ongoing support. The lack of patch links suggests that a fix may be pending or that organizations should seek out vendor advisories for mitigation steps. This vulnerability underscores the importance of timely patching and minimizing local access to sensitive systems.

For European organizations, the impact of CVE-2025-55696 is significant, particularly for enterprises and government agencies that still operate Windows 10 Version 1809 in their environments. Successful exploitation can lead to unauthorized privilege escalation, enabling attackers to bypass security controls, access sensitive data, install persistent malware, or disrupt critical services. This is especially concerning for sectors such as finance, healthcare, energy, and public administration, where data confidentiality and system integrity are paramount. The vulnerability could facilitate lateral movement within networks, increasing the risk of widespread compromise. Given the local attack vector, insider threats or compromised user accounts pose a heightened risk. Additionally, organizations with legacy systems or delayed patch management cycles are more vulnerable. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits rapidly once details are public. The overall impact includes potential regulatory and compliance violations under GDPR if personal data is exposed due to privilege escalation attacks.

1. Apply official patches or security updates from Microsoft as soon as they become available for Windows 10 Version 1809. 2. If patches are not yet available, restrict local administrative access and limit user permissions to the minimum necessary to reduce the attack surface. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious privilege escalation attempts. 4. Harden systems by disabling unnecessary services and enforcing strict access controls on sensitive resources. 5. Conduct regular audits of user accounts and privileges to detect and remove excessive permissions. 6. Implement network segmentation to contain potential compromises and prevent lateral movement. 7. Educate users about the risks of local privilege escalation and enforce policies to prevent unauthorized software installations or execution. 8. Monitor system logs for anomalies related to token manipulation or unusual calls to NtQueryInformationToken. 9. Consider upgrading to a supported and fully patched Windows version to reduce exposure to legacy vulnerabilities. 10. Maintain an incident response plan that includes procedures for privilege escalation attacks.