Table of Contents
- What Critical Fixes Were Included in Microsoft’s Latest Patch Tuesday?
- December 2025 Security Rollout
- Windows Lifecycle and Licensing Changes
- Critical Vulnerabilities: What You Need to Patch Now
- The Zero-Day Threat (Immediate Action Required)
- The Development Risk
- The Publicly Disclosed Flaw
- The Core Kernel Vulnerability
- The “No-Click” Office Threats
- Strategic Recommendations
What Critical Fixes Were Included in Microsoft’s Latest Patch Tuesday?
As an advisor helping you navigate the complexities of cybersecurity, I want to ensure you fully understand the implications of the December 9, 2025, Microsoft Patch Tuesday release. Ignoring these updates leaves your infrastructure exposed to active threats, including a zero-day exploit currently used in the wild.
This guide breaks down the critical patches, the affected systems, and the specific actions you must take immediately to secure your environment.
December 2025 Security Rollout
Microsoft’s final major security release of 2025 addresses 56 distinct vulnerabilities (CVEs) across its ecosystem, spanning Windows clients, servers, Office suites, and development tools.
The most urgent takeaway is the presence of a zero-day vulnerability. In cybersecurity terms, this means attackers discovered and utilized the flaw before Microsoft could release a fix. Patching this specific vulnerability is not optional; it is an emergency requirement.
Windows Lifecycle and Licensing Changes
Before diving into specific exploits, you must verify your current support status. The landscape for Windows 10 and Server 2012 has shifted significantly this year.
- Windows 10/11 & Server Counterparts: These updates remain cumulative. Installing the December package applies all previous security and non-security fixes, ensuring your system is up to date in a single step.
- Windows 10 Version 22H2: Support for this version ended in October 2025. If you are still running 22H2 without an Extended Security Updates (ESU) license, you did not receive this month’s security patches. You are now operating an unprotected system.
- Windows Server 2012 R2: Similar to Windows 10 22H2, standard support has ceased. You must have an active ESU license to access the December fixes. This ESU coverage will continue until October 2026.
Critical Vulnerabilities: What You Need to Patch Now
The following vulnerabilities represent the highest risk to your organization. I have prioritized these based on severity and exploitability.
The Zero-Day Threat (Immediate Action Required)
CVE-2025-62221: Windows Cloud Files Mini Filter Driver Elevation of Privilege
Severity: Important (CVSS 7.8)
The Risk: Attackers are actively using this flaw right now. It affects the Cloud Files Mini Filter Driver. If a bad actor has local access to a machine (even with low privileges), they can exploit this bug to elevate themselves to SYSTEM privileges.
The Consequence: Gaining SYSTEM access gives an attacker total control over the machine, allowing them to install programs, view data, and create new accounts with full user rights.
The Development Risk
CVE-2025-64671: GitHub Copilot for JetBrains Remote Code Execution
Severity: Important (CVSS 8.4)
The Risk: Dubbed “IDEsaster,” this flaw exists within the GitHub Copilot plugin for JetBrains IDEs. It involves a command injection vulnerability.
The Attack Vector: An attacker uses a “malicious cross-prompt injection” via an untrusted file or MCP server. If your terminal has “Auto-Approve” enabled, the attacker can append unauthorized commands to legitimate ones.
Implication: While rated “unlikely” to be exploited, the high score and the potential for Remote Code Execution (RCE) make this a priority for development teams.
The Publicly Disclosed Flaw
CVE-2025-54100: PowerShell Remote Code Execution
Severity: Important (CVSS 7.8)
The Risk: Details of this vulnerability were public before the fix was released, increasing the likelihood of attempted exploits.
The Fix Behavior: Post-update, you will notice a behavior change. The system will now display a warning message whenever the Invoke-WebRequest command is used, adding a layer of friction to prevent silent malicious scripts from running.
The Core Kernel Vulnerability
CVE-2025-62458: Win32k Elevation of Privilege
Severity: Important (CVSS 7.8)
The Risk: This affects the Win32k driver, a core component of the Windows kernel.
Likelihood: Microsoft rates exploitation as “likely.”
The Consequence: Similar to the zero-day mentioned above, successful exploitation grants SYSTEM privileges. Because Win32k is ubiquitous in Windows environments, the attack surface is wide.
The “No-Click” Office Threats
CVE-2025-62554 & CVE-2025-62557: Microsoft Office Remote Code Execution
Severity: Critical (CVSS 8.4)
The Risk: These are particularly dangerous because they involve the “Preview Pane” attack vector.
The Attack: You do not need to open a malicious file to be infected. Simply selecting a specially crafted Office document in Windows Explorer (so that it renders in the Preview Pane) triggers the exploit.
Note for Mac Users: Updates for Microsoft Office LTSC for Mac are currently delayed. You must monitor official channels closely for their release.
Strategic Recommendations
- Audit Your ESU Status: Ensure all Windows 10 22H2 and Server 2012 R2 endpoints have active Extended Security Update licenses. Without them, you are blind to these updates.
- Prioritize the Zero-Day: Push the patch for CVE-2025-62221 to all workstations immediately.
- Disable Preview Panes: As a temporary mitigation for the Office vulnerabilities, consider enforcing a Group Policy to disable the Preview Pane in Windows Explorer until patching is confirmed.
- Warn Developers: Alert your development teams using JetBrains and Copilot about the potential risk of untrusted files and the “Auto-Approve” terminal setting.