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 17763.0). The flaw exists in the NtQueryInformationToken function, part of the Windows kernel's native API (ntifs.h), which handles querying information about access tokens. The race condition occurs when the system checks a security condition and then uses the result without ensuring the state remains unchanged, allowing an attacker to manipulate the timing between these operations. This can lead to an attacker with authorized local access escalating their privileges by exploiting the window between check and use. The vulnerability does not require user interaction but does require local privileges, meaning the attacker must already have some level of access to the system. The CVSS 3.1 score of 7.8 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction needed. No public exploit code or patches are currently available, increasing the urgency for defensive measures. The vulnerability is particularly dangerous because privilege escalation can enable attackers to bypass security controls, install persistent malware, or access sensitive data.

For European organizations, this vulnerability poses a significant risk, especially those still operating legacy Windows 10 Version 1809 systems, which are common in enterprise and government environments due to long upgrade cycles. Successful exploitation allows attackers to elevate privileges locally, potentially leading to full system compromise. This can result in unauthorized access to confidential data, disruption of critical services, and the ability to deploy ransomware or other malware with elevated rights. The impact is heightened in sectors such as finance, healthcare, government, and critical infrastructure, where data sensitivity and operational continuity are paramount. Additionally, the lack of available patches means organizations must rely on compensating controls, increasing operational complexity and risk. The vulnerability could also facilitate lateral movement within networks, amplifying the scope of compromise.

Given the absence of official patches, European organizations should implement the following specific mitigations: 1) Restrict local user privileges rigorously, ensuring users operate with the least privilege necessary to reduce the pool of potential attackers. 2) Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious local activities indicative of privilege escalation attempts. 3) Harden system configurations by disabling or limiting access to sensitive APIs and functions where possible, including restricting access to NtQueryInformationToken calls through security policies or kernel-level monitoring. 4) Enforce strict auditing and logging of privilege-related events to detect early signs of exploitation attempts. 5) Accelerate migration off Windows 10 Version 1809 to supported and patched Windows versions to eliminate exposure. 6) Use network segmentation to limit lateral movement opportunities if a local compromise occurs. 7) Educate IT staff and users about the risks of local privilege escalation and the importance of maintaining updated systems.