CVE-2025-54091 is an integer overflow vulnerability classified under CWE-190, found in the Hyper-V virtualization component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw arises when an integer value used internally by Hyper-V improperly wraps around due to exceeding its maximum value, causing unexpected behavior in memory management or logic flow. This can be exploited by an attacker with local access and limited privileges to escalate their privileges to SYSTEM or equivalent, thereby gaining full control over the host system. The vulnerability does not require user interaction, but it does require the attacker to have some level of local authorization, such as a standard user account. The CVSS v3.1 base score of 7.8 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and low privileges required. Although no public exploits or patches are currently available, the vulnerability poses a significant risk to environments where Windows 10 1809 is still in use, particularly those leveraging Hyper-V for virtualization. The absence of patches necessitates immediate mitigation efforts to prevent exploitation. This vulnerability is particularly critical because Hyper-V is often used in enterprise environments to host virtual machines, and a successful exploit could compromise multiple virtualized workloads or the host itself.

For European organizations, the impact of CVE-2025-54091 can be severe. Successful exploitation allows attackers to elevate privileges locally, potentially gaining SYSTEM-level access on critical servers or workstations running Windows 10 1809 with Hyper-V enabled. This can lead to unauthorized access to sensitive data, disruption of services, and the ability to deploy further malware or ransomware. Organizations relying on legacy Windows 10 systems in sectors such as finance, healthcare, government, and critical infrastructure are particularly vulnerable. The virtualization aspect increases risk since compromising the host can affect multiple virtual machines, amplifying the damage. Additionally, the lack of available patches means organizations must rely on interim mitigations, increasing operational complexity and risk exposure. The vulnerability could also be leveraged in targeted attacks against European entities with high-value assets or strategic importance, potentially impacting national security or economic stability.

1. Restrict local access: Limit the number of users with local access to systems running Windows 10 Version 1809 with Hyper-V enabled. Use strict access controls and monitor for unauthorized access attempts. 2. Disable Hyper-V if not required: If virtualization is not essential on affected systems, disable the Hyper-V feature to eliminate the attack surface. 3. Upgrade to supported Windows versions: Prioritize upgrading affected systems to newer, supported Windows versions where this vulnerability is not present. 4. Implement application whitelisting and endpoint detection: Use advanced endpoint protection to detect suspicious privilege escalation attempts and block unauthorized code execution. 5. Monitor system logs and Hyper-V activity: Establish enhanced logging and monitoring to detect anomalous behavior indicative of exploitation attempts. 6. Network segmentation: Isolate critical systems running legacy Windows 10 to limit lateral movement in case of compromise. 7. Prepare incident response plans: Ensure readiness to respond quickly to any detected exploitation attempts, including containment and remediation procedures. 8. Stay informed: Monitor Microsoft security advisories for patches or updates related to this vulnerability and apply them promptly once available.