In December 2025, Microsoft issued security updates for 56 vulnerabilities affecting various Windows components, including three critical and two zero-day flaws. The most notable zero-day, CVE-2025-62221 (CVSS 7.8), is a use-after-free vulnerability in the Windows Cloud Files Mini Filter Driver, a core component that integrates with cloud storage services like OneDrive, Google Drive, and iCloud. This flaw allows an authorized attacker with local access to escalate privileges to SYSTEM level by exploiting the minifilter driver’s handling of file system requests. Although exploitation requires initial access, threat actors can chain this vulnerability with other attack vectors such as phishing or remote code execution flaws to gain full control over affected systems. The vulnerability enables attackers to deploy kernel-level components or signed drivers, facilitating stealthy persistence and potential domain-wide compromise when combined with credential theft. Microsoft’s Threat Intelligence Center and Security Response Center discovered and reported this flaw. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added CVE-2025-62221 to its Known Exploited Vulnerabilities catalog, enforcing patching deadlines for federal agencies. Additionally, two other zero-days were disclosed: CVE-2025-54100, a command injection vulnerability in Windows PowerShell that allows unauthenticated code execution via crafted web content processed by Invoke-WebRequest; and CVE-2025-64671, a command injection flaw in GitHub Copilot for JetBrains IDE, enabling unauthorized local code execution through prompt injection attacks. These vulnerabilities highlight emerging risks associated with AI-assisted development tools and cloud integration components. Microsoft and other vendors have released patches, but exploitation risks remain high until systems are updated. The broad range of affected components and the active exploitation of CVE-2025-62221 underscore the criticality of timely remediation.

European organizations face significant risks from these vulnerabilities due to widespread Windows usage in enterprise environments and reliance on cloud storage integrations. The actively exploited CVE-2025-62221 can lead to full system compromise, enabling attackers to deploy kernel-level malware, evade detection, and move laterally within networks. This threatens confidentiality through data theft, integrity via unauthorized system modifications, and availability by potential denial-of-service or ransomware deployment. The PowerShell and GitHub Copilot zero-days increase the attack surface by allowing remote or local code execution without authentication, potentially enabling attackers to bypass security controls via social engineering or malicious code injection. Critical infrastructure, government agencies, financial institutions, and large enterprises in Europe are particularly vulnerable due to their reliance on Windows ecosystems and cloud services. The potential for domain-wide compromise elevates the risk of widespread disruption and data breaches. Failure to patch promptly could result in exploitation campaigns targeting European entities, especially given geopolitical tensions and the attractiveness of European data and infrastructure to threat actors.

European organizations should prioritize immediate deployment of Microsoft’s December 2025 security updates, focusing on the patch for CVE-2025-62221 due to its active exploitation status. Implement strict access controls and monitoring to detect unusual privilege escalation attempts, especially on systems running cloud storage integrations. Employ endpoint detection and response (EDR) solutions capable of identifying kernel-level anomalies and suspicious driver loads. For the PowerShell vulnerability (CVE-2025-54100), restrict or monitor the use of Invoke-WebRequest and other PowerShell commands that process web content, and educate users about phishing and social engineering risks. Review and harden configurations of AI-assisted development tools like GitHub Copilot, applying vendor patches and limiting their use in sensitive environments. Conduct threat hunting for indicators of compromise related to these vulnerabilities and implement network segmentation to contain potential lateral movement. Maintain up-to-date backups and incident response plans to mitigate impact in case of compromise. Collaborate with national cybersecurity agencies for threat intelligence sharing and guidance.