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, part of the Windows kernel's native API (ntifs.h), which handles querying security token information. The TOCTOU race condition occurs when the system checks a condition and then uses the result later, but an attacker can manipulate the state between these two operations, leading to inconsistent or unauthorized behavior. In this case, an authorized local attacker with limited privileges can exploit the race window to elevate their privileges, potentially gaining SYSTEM-level access. This elevation compromises system confidentiality, integrity, and availability. The vulnerability does not require user interaction and has a low attack complexity, but requires local access and some privileges. The CVSS v3.1 base score is 7.8, reflecting high severity with high impact on confidentiality, integrity, and availability. No public exploits or patches are currently available, but the vulnerability is published and reserved since August 2025. The affected Windows 10 Version 1809 remains in use in many enterprise and industrial environments, increasing the risk of exploitation. The vulnerability is significant because privilege escalation is a common step in multi-stage attacks, enabling attackers to bypass security controls and gain full control over affected systems.

The primary impact of CVE-2025-55696 is local privilege escalation, allowing attackers with limited access to gain elevated privileges, potentially SYSTEM-level. This can lead to full system compromise, unauthorized access to sensitive data, installation of persistent malware, disabling security controls, and disruption of system availability. Organizations running Windows 10 Version 1809, especially in enterprise, government, and critical infrastructure sectors, face increased risk of targeted attacks leveraging this vulnerability. The flaw could be chained with other vulnerabilities or used by insider threats to bypass security policies. Since Windows 10 1809 is still widely deployed in many organizations, the scope of affected systems is substantial. The lack of required user interaction and low complexity of exploitation further increase the threat. Although no known exploits are currently in the wild, the vulnerability's characteristics make it a likely target for future exploitation, especially by advanced persistent threat (APT) groups and cybercriminals seeking privilege escalation capabilities.

1. Apply official Microsoft patches immediately once released for Windows 10 Version 1809 to remediate the TOCTOU race condition in NtQueryInformationToken. 2. Until patches are available, restrict local access to systems running Windows 10 1809 by enforcing strict access controls and limiting administrative privileges. 3. Employ endpoint detection and response (EDR) solutions to monitor for unusual privilege escalation attempts or suspicious behavior related to token manipulation. 4. Use application whitelisting and least privilege principles to reduce the attack surface and prevent unauthorized code execution. 5. Regularly audit and review user accounts and permissions to ensure no unnecessary privileges are granted. 6. Implement network segmentation to isolate critical systems and reduce lateral movement opportunities. 7. Educate system administrators and security teams about this vulnerability and encourage proactive monitoring of security advisories from Microsoft. 8. Consider upgrading affected systems to a supported and patched Windows version if feasible, as Windows 10 Version 1809 is an older release with limited ongoing support.