Microsoft released its final Patch Tuesday of 2025 on December 9, addressing 57 security vulnerabilities across Windows, Office, Exchange Server, Azure, PowerShell, and Windows Defender. The release includes one actively exploited zero-day, two publicly disclosed vulnerabilities, and two critical remote code execution flaws.
With this release, Microsoft patched a total of 1,129 vulnerabilities in 2025 — an 11.9% increase over 2024 and a sign of the expanding attack surface across the Microsoft ecosystem.
The Zero-Day: CVE-2025-62221
The actively exploited vulnerability is a use-after-free flaw in the Windows Cloud Files Mini Filter Driver (CVE-2025-62221). Microsoft confirmed exploitation in the wild, and CISA added it to the Known Exploited Vulnerabilities catalog with a remediation deadline of December 30, 2025. Successful exploitation grants SYSTEM-level privileges, making this a priority for any organization running supported versions of Windows.
Critical Vulnerabilities
Two critical remote code execution flaws in Microsoft Office (CVE-2025-62554 and CVE-2025-62557) allow arbitrary code execution when a user opens a malicious Office document. The preview pane is a viable attack vector for CVE-2025-62554, meaning users don't even need to fully open the file to be compromised. These are prime candidates for phishing campaigns and should be patched immediately on all desktop and Citrix/RDS environments.
Windows Routing and Remote Access Service (RRAS) received fixes for two more critical RCE vulnerabilities (CVE-2025-62549 and CVE-2025-64678). Any server running RRAS, DirectAccess, or legacy VPN roles is exposed to unauthenticated remote code execution via specially crafted network packets.
Other Notable Fixes
A command injection vulnerability in Windows PowerShell now triggers a security confirmation prompt when using Invoke-WebRequest, warning users about potential script execution risks. This is a behavioral change that may affect automation scripts — test your PowerShell-based workflows before deploying broadly.
Exchange Server received a fix for CVE-2025-64666, an elevation of privilege vulnerability that allows authenticated low-privilege users to gain administrator rights. Exchange 2016/2019 fixes are only available through the Extended Security Update program — organizations still running these versions without ESU should accelerate their migration to Exchange Server Subscription Edition.
The GitHub Copilot Plugin for JetBrains received a fix for CVE-2025-64671, a remote code execution flaw that allowed attackers to execute arbitrary code by tricking the LLM into running commands that bypass the user's auto-approve settings. This is a notable entry as AI-assisted development tools become a new attack surface.
Deployment Recommendations
Microsoft paused optional preview updates for December due to reduced holiday activity, so this month's security-only focus simplifies deployment. Prioritize the actively exploited Cloud Files Mini Filter Driver vulnerability and the two Office RCE flaws. Test PowerShell workflow impacts from the Invoke-WebRequest prompt change before broad deployment.
With 1,129 CVEs patched across 2025, organizations without automated patch management and validation workflows are falling further behind. Every month that passes without ring-based deployment and compliance verification increases exposure to the compounding backlog of unpatched vulnerabilities.