CVE-2025-54093 is a high-severity vulnerability identified as a Time-of-check Time-of-use (TOCTOU) race condition in the TCP/IP stack of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises when the system improperly handles the timing between checking a condition and using the result of that check, allowing an attacker to exploit the window of inconsistency. Specifically, an authorized local attacker with limited privileges can leverage this race condition to elevate their privileges on the affected system. The vulnerability is categorized under CWE-367, which relates to TOCTOU race conditions that can lead to security issues such as privilege escalation. The CVSS v3.1 base score is 7.0, indicating a high severity level, with the vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C. This means the attack requires local access (AV:L), high attack complexity (AC:H), low privileges (PR:L), no user interaction (UI:N), and impacts confidentiality, integrity, and availability to a high degree (C:H/I:H/A:H). The scope is unchanged (S:U), and the exploit code maturity is official (RL:O) with confirmed remediation (RC:C). No known exploits are currently reported in the wild, and no patches or mitigations have been linked yet. The vulnerability affects Windows 10 Version 1809, which is an older version of Windows 10, but still in use in some environments. The nature of the vulnerability allows an attacker who already has some level of access to the system to escalate privileges, potentially gaining full control over the system, which could lead to unauthorized data access, system manipulation, or disruption of services.

For European organizations, this vulnerability poses a significant risk, especially in environments where Windows 10 Version 1809 is still deployed, such as legacy systems in industrial, governmental, or enterprise settings. Successful exploitation could allow attackers to escalate privileges from a limited user account to SYSTEM or administrative level, enabling them to bypass security controls, access sensitive data, install persistent malware, or disrupt critical services. This is particularly concerning for sectors with strict data protection requirements under GDPR, as unauthorized access or data breaches could lead to regulatory penalties and reputational damage. Additionally, the high impact on confidentiality, integrity, and availability means that critical infrastructure relying on affected systems could face operational disruptions. Although exploitation requires local access and has high complexity, insider threats or attackers who gain initial footholds through other means could leverage this vulnerability to deepen their control. The absence of known exploits in the wild currently reduces immediate risk, but the lack of available patches means organizations remain exposed until remediation is applied.

European organizations should prioritize the following specific mitigation steps: 1) Identify and inventory all systems running Windows 10 Version 1809 to assess exposure. 2) Apply any available security updates or patches from Microsoft as soon as they are released; monitor official Microsoft security advisories closely. 3) If patches are not yet available, implement strict access controls to limit local user privileges and restrict the ability to execute untrusted code or scripts. 4) Employ application whitelisting and endpoint detection and response (EDR) solutions to detect unusual privilege escalation attempts or race condition exploitation patterns. 5) Conduct regular security audits and user privilege reviews to minimize the number of users with local access rights. 6) Consider upgrading affected systems to a more recent, supported Windows version where this vulnerability is not present. 7) Enhance monitoring of system logs and network activity for signs of suspicious behavior indicative of exploitation attempts. 8) Educate IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of adhering to least privilege principles. These targeted actions go beyond generic advice by focusing on controlling local access, monitoring for exploitation indicators, and accelerating patch deployment or system upgrades.