Microsoft concluded 2025 with a massive security update that cybersecurity teams cannot ignore.
Released yesterday (Dec. 9) as cumulative update KB5072033, this security patch addresses 57 vulnerabilities across Windows systems and Office applications—including one actively exploited zero-day that hackers are weaponizing right now.
With over 1,100 vulnerabilities patched in 2025 alone, this December release caps off a year of unprecedented security challenges. Organizations still running legacy systems face mounting pressure, especially following Windows 10’s end-of-life in October, while attackers continue targeting fundamental Windows components with increasingly sophisticated attacks.
The zero-day that’s already under attack
The most urgent flaw demanding immediate attention is CVE-2025-62221, a privilege escalation vulnerability in the Windows Cloud Files Mini Filter Driver that attackers are actively exploiting in the wild. Microsoft’s security teams confirmed this use-after-free memory corruption issue allows attackers with minimal system access to escalate privileges to SYSTEM-level control, carrying a CVSS score of 7.8.
What makes this particularly dangerous is how hackers weaponize the flaw in multi-stage attacks. Security researchers warn that attackers can chain CVE-2025-62221 with other weaknesses to escalate from low-privileged access to complete system dominance. Microsoft’s Threat Intelligence Center and Security Response Center jointly identified the exploit after detecting active abuse in real-world attacks, underscoring the immediate danger this vulnerability poses to unpatched systems.
Two additional zero-day vulnerabilities complete the urgent fixes. CVE-2025-64671 targets GitHub Copilot for JetBrains with an 8.4 CVSS rating, enabling command injection through malicious prompts. The PowerShell vulnerability CVE-2025-54100 allows automatic script execution when webpages are retrieved using Invoke-WebRequest, though Microsoft has added warning prompts to mitigate this risk.
Beyond the zero-days, yesterday’s update addresses multiple critical remote code execution vulnerabilities that could allow complete system compromise over networks. Two Microsoft Office vulnerabilities, CVE-2025-62554 and CVE-2025-62557, both carry 8.4 CVSS scores and enable remote attackers to execute arbitrary code through malicious documents. These Office-targeting flaws represent particular risks in enterprise environments where document sharing is routine.
The update also patches CVE-2025-62549, a highly dangerous flaw in the Routing and Remote Access Service that permits network-based code execution without any prior authentication. This type of vulnerability gives attackers direct pathways into corporate networks, making it a prime target for advanced persistent threat groups seeking initial access to enterprise environments.
Microsoft’s vulnerability breakdown reveals the scope of this month’s security challenges: 28 elevation of privilege issues, 19 remote code execution flaws, four information disclosure vulnerabilities, three denial of service bugs, and two spoofing vulnerabilities. The concentration of privilege escalation and remote execution flaws indicates sophisticated attack chains targeting both initial access and lateral movement within compromised networks.
What security teams must do right now
Organizations need to treat yesterday’s Patch Tuesday as an emergency security response. Microsoft recommends immediate installation through Settings > Windows Update > Check for updates, with mandatory system reboots required for changes to take effect. The update affects Windows 10 ESU systems, Windows 11 versions 24H2 and 25H2, all supported Windows Server editions, Microsoft Office applications, Exchange Server, and various Azure components.
Security experts emphasize that organizations should prioritize systems affected by CVE-2025-62221 given its active exploitation status. Developer environments using GitHub Copilot require immediate updates, while PowerShell deployments need script reviews and restricted access policies. The update includes quality-of-life improvements like fixes for Copilot UI bugs, File Explorer visual glitches, and critical networking issues affecting virtual switches after host reboots.
Yesterday’s December release caps off a year of unprecedented security challenges. As attackers increasingly target cloud integration points, AI-enhanced development tools, and core Windows components, automated patch management has evolved from convenience to survival necessity for modern enterprise security operations.
Microsoft recently, and quietly, issued another Windows 11 update it classifies as “critical.”
