December Patch Tuesday - Three Microsoft Zero-Days Fixed
CORTEX Protocol Intelligence Assessment
Business Impact: Three zero-days exploited in wild before Patch Tuesday indicates active campaigns targeting Windows infrastructure and developer tools. Cloud Files driver privilege escalation enables full system compromise. GitHub Copilot RCE affects developer environments, potential supply chain vector. PowerShell RCE continues trend of living-off-the-land attack enablers. Technical Context: CVE-2025-62221 is privilege escalation in Windows Cloud Files Mini Filter Driver (T1068 Exploitation for Privilege Escalation). CVE-2025-64671 targets GitHub Copilot for JetBrains IDE integration (T1195.001 Supply Chain Compromise). CVE-2025-54100 exploits PowerShell scripting engine (T1059.001). Microsoft's Invoke-WebRequest warning directly addresses ClickFix abuse pattern observed in CastleLoader and similar campaigns. All three confirmed exploited before disclosure.
Strategic Intelligence Guidance
- Deploy December Patch Tuesday updates across all supported Windows client and server versions as a high-priority change window, focusing first on internet-exposed and high-value systems.
- Harden PowerShell usage by enforcing execution policies, requiring signed scripts, and monitoring for suspicious Invoke-WebRequest activity that pulls code from untrusted domains.
- Review use of GitHub Copilot for JetBrains in development environments, ensure the CVE-2025-64671 patch is applied, and monitor plugin usage for unusual network or file activity.
- Integrate exploitation of privilege escalation and PowerShell RCE vulnerabilities into threat modeling and red team exercises to validate that EDR and monitoring controls detect likely attack chains.