CVE-2026-20940 is a vulnerability classified under CWE-822 (Untrusted Pointer Dereference) affecting the Windows Cloud Files Mini Filter Driver component in Microsoft Windows 10 Version 22H2 (build 19045.0). The flaw is a heap-based buffer overflow that occurs when the driver improperly handles pointers, leading to memory corruption. An authorized attacker with local access can exploit this vulnerability to execute arbitrary code with elevated privileges, effectively escalating from a lower-privileged user to SYSTEM level. The attack vector requires local access but no user interaction, making it a potent privilege escalation vector once initial access is gained. The vulnerability impacts confidentiality, integrity, and availability by allowing full control over the affected system. The CVSS v3.1 base score is 7.8, reflecting high severity due to low attack complexity, low privileges required, and high impact on system security. No public exploits have been reported yet, and no official patches are linked, indicating organizations should be vigilant for forthcoming updates. The Cloud Files Mini Filter Driver is involved in managing cloud file synchronization and caching, a component commonly present in enterprise Windows 10 deployments, increasing the potential attack surface. This vulnerability is particularly critical in environments where local user accounts have some access but should not have administrative privileges.

For European organizations, the impact of CVE-2026-20940 is significant. Successful exploitation allows attackers to escalate privileges locally, 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. Organizations relying on Windows 10 Version 22H2, especially in sectors like finance, healthcare, government, and critical infrastructure, face increased risk of data breaches and operational disruption. The vulnerability could be leveraged in multi-stage attacks where initial access is gained through phishing or insider threats, then escalated to full control. The absence of user interaction requirement and the low complexity of exploitation increase the likelihood of exploitation in targeted attacks. Additionally, the Cloud Files Mini Filter Driver’s role in cloud file synchronization means that compromise could affect data integrity and availability across hybrid cloud environments, impacting business continuity and compliance with data protection regulations such as GDPR.

1. Apply official Microsoft patches immediately once they become available to remediate the vulnerability. 2. Until patches are released, restrict local user access to systems running Windows 10 Version 22H2, especially limiting administrative privileges. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious activities related to the Cloud Files Mini Filter Driver. 4. Audit and harden local user accounts, removing unnecessary privileges and enforcing least privilege principles. 5. Monitor system logs and security events for anomalies indicating attempts to exploit local privilege escalation vulnerabilities. 6. Consider disabling or restricting the Cloud Files Mini Filter Driver if it is not essential for business operations, after assessing operational impact. 7. Educate IT staff and users about the risks of local privilege escalation and the importance of maintaining updated systems. 8. Implement network segmentation to limit lateral movement if a local compromise occurs. 9. Regularly review and update incident response plans to include scenarios involving local privilege escalation exploits.