CVE-2025-55696 is a vulnerability classified under CWE-367, a time-of-check to time-of-use (TOCTOU) race condition, found in the NtQueryInformationToken function of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This function is responsible for querying token information related to security contexts and access rights. The race condition occurs because the system checks certain security attributes at one point in time but uses them later without re-verifying, allowing an attacker to manipulate the state between these two operations. This flaw can be exploited by an authorized local attacker who has limited privileges to escalate their rights to SYSTEM or equivalent, thereby gaining full control over the machine. The vulnerability affects confidentiality, integrity, and availability as it allows bypassing of security boundaries. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local, low attack complexity, and requiring privileges but no user interaction. Although no known exploits are currently in the wild, the vulnerability is critical enough to warrant immediate attention. The lack of available patches at the time of publication means organizations must rely on interim mitigations and monitoring. This vulnerability is particularly dangerous in environments where Windows 10 Version 1809 remains in use, especially in enterprise and industrial control systems where privilege escalation can lead to significant operational disruption or data breaches.

For European organizations, the impact of CVE-2025-55696 can be significant. Many enterprises and government agencies still operate legacy Windows 10 Version 1809 systems due to compatibility or operational constraints. Exploitation of this vulnerability allows attackers with local access to elevate privileges, potentially leading to full system compromise. 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 finance, healthcare, manufacturing, and critical infrastructure are particularly vulnerable due to the high value of their data and systems. Additionally, the vulnerability could be leveraged in targeted attacks or insider threat scenarios. The absence of public exploits reduces immediate risk but does not eliminate it, especially as threat actors may develop exploits over time. The high severity score reflects the broad impact on confidentiality, integrity, and availability, making this a priority for European organizations to address promptly.

1. Apply official Microsoft patches as soon as they become available for Windows 10 Version 1809. 2. Restrict local access to systems running the affected OS version by enforcing strict access controls and using network segmentation to limit exposure. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious privilege escalation attempts. 4. Regularly audit user privileges and remove unnecessary local administrative rights to reduce the attack surface. 5. Implement strict logging and monitoring of security events related to token queries and privilege changes to detect potential exploitation attempts early. 6. Consider upgrading affected systems to a supported, more secure Windows version if operationally feasible to eliminate exposure to this and other legacy vulnerabilities. 7. Educate IT staff and users about the risks of local privilege escalation and the importance of maintaining updated systems. 8. Use virtualization or sandboxing techniques for high-risk applications to contain potential exploitation.