Microsoft Patch Tuesday December 2025: 56 Security Fixes

The latest Microsoft Patch Tuesday delivered a comprehensive set of security updates that address 56 critical and high‑severity vulnerabilities across Windows, Office, and several Microsoft‑supported applications. With this release, the company continues its commitment to patching the most pressing weaknesses, including a zero‑day flaw that was actively exploited in the wild and a series of privilege‑escalation bugs that could allow attackers to gain elevated rights on targeted systems.

Zero‑Day CVE‑2025‑62221: Immediate Threat

At the heart of the update is CVE‑2025‑62221, a zero‑day vulnerability that enables remote privilege escalation in the Windows Cloud Files Mini Filter Driver. This driver is integral to cloud storage integration for OneDrive, Google Drive, and iCloud, making the flaw relevant to a wide range of Windows users. The vulnerability can be triggered by a crafted file that, when accessed through the filter, grants an attacker elevated permissions without requiring user interaction.

Microsoft’s advisory notes that the flaw is currently being exploited in the field. The patch, available through Windows Update and the Microsoft Update Catalog, must be installed immediately to prevent potential compromise of corporate and personal machines.

Critical Office Bugs: CVE‑2025‑62554, CVE‑2025‑62557, CVE‑2025‑62562

Three additional vulnerabilities affecting Microsoft Office and Outlook were classified as “critical.” Both CVE‑2025‑62554 and CVE‑2025‑62557 can be triggered by simply opening a malicious email attachment or previewing a corrupted message in the Preview Pane. While the Outlook preview pane is not an attack vector for CVE‑2025‑62562, the flaw still allows arbitrary code execution when a user opens a specially crafted message. The rapid deployment of patches for these bugs underscores Microsoft’s focus on protecting email users from spear‑phishing and malicious content.

How to Safeguard Email Users

• Disable the Preview Pane in Outlook for an extra layer of protection.
• Configure email clients to open attachments in a sandboxed environment.
• Keep Office 365 and Outlook updated with the latest security patches.

Privilege Escalation Flaws Across Windows Components

Beyond the high‑profile Office bugs, the December patch set includes a series of non‑critical but highly likely-to-be-exploited privilege‑escalation vulnerabilities. These affect core Windows drivers and services such as Win32k (CVE‑2025‑62458), the Common Log File System Driver (CVE‑2025‑62470), Remote Access Connection Manager (CVE‑2025‑62472), and the Storage VSP Driver (CVE‑2025‑59516 & CVE‑2025‑59517). Each of these bugs could allow an attacker with local or network access to gain elevated privileges, potentially bypassing user authentication controls.

Recommended Mitigation Steps

1. Apply the latest Windows updates promptly through Windows Update or the Microsoft Update Catalog.
2. Enable User Account Control (UAC) to restrict the execution of privileged code.
3. Implement least‑privilege policies for network services and user accounts.

GitHub Copilot Plugin Vulnerability: CVE‑2025‑64671

One of the most intriguing fixes in this batch is CVE‑2025‑64671, a remote code execution flaw in the GitHub Copilot Plugin for JetBrains. The vulnerability allows a maliciously crafted prompt to trick the large language model (LLM) into executing arbitrary commands that bypass the plugin’s auto‑approve settings. The issue is part of a broader set of vulnerabilities, collectively dubbed IDE saster, affecting popular AI coding assistants such as Cursor, WindSrf, Gemini CLI, and Claude Code.

Developers using the Copilot plugin should update to the latest version immediately and review their code review processes to ensure that auto‑generated code does not contain unintended execution paths. For more information, see the official Microsoft Security Response Center entry on CVE‑2025‑64671.

Windows PowerShell RCE: CVE‑2025‑54100

The December rollout also addresses a remote code execution vulnerability in Windows PowerShell (CVE‑2025‑54100). This flaw allows an unauthenticated attacker to execute code in the security context of a user on Windows Server 2008 and newer. PowerShell is a powerful automation tool, and the potential for abuse in this context is significant, particularly in environments where scripts are run with elevated privileges.

Administrators should restrict the use of PowerShell by implementing AppLocker or other execution policies, and ensure that the latest updates are installed on all server machines.

Applying the Updates: Step‑by‑Step Guide

To maintain a secure environment, follow these steps to install the December patch set:

1. Open Windows Update and check for the latest updates. The patch will be listed under the “Security Updates” section.
2. Download and install the updates. For servers, use the Microsoft Update Catalog to download the specific .msu files.
3. Restart the system to complete the installation. Many of the updates require a reboot to apply kernel‑level changes.
4. Verify installation by running the Windows Update Troubleshooter or checking the “Installed Updates” list in the Control Panel.

For a detailed breakdown of each update and its associated CVE, refer to the SANS Internet Storm Center’s comprehensive post on Microsoft Patch Tuesday December 2025.

Impact on Business and End Users

While the majority of the vulnerabilities were not actively exploited at the time of release, the cumulative risk is significant. Attackers could chain multiple exploits to move laterally across a network, elevate privileges, and ultimately exfiltrate sensitive data. The presence of a zero‑day flaw, in particular, signals that adversaries may already be targeting vulnerable systems.

Organizations should adopt a layered defense strategy, combining timely patching with network segmentation, intrusion detection, and user education. Employees should be trained to recognize suspicious emails and avoid opening attachments from unknown sources.

Security Recommendations for 2025 and Beyond

• Implement a rigorous patch management policy that prioritizes critical and high‑severity updates.
• Leverage Microsoft Defender for Endpoint to detect exploitation attempts in real time.
• Use application whitelisting to restrict execution of unapproved binaries.
• Regularly audit system logs for anomalous privilege escalation attempts.

Conclusion

The December 2025 Microsoft Patch Tuesday demonstrates the company’s ongoing dedication to securing its software ecosystem. With 56 fixes—including a zero‑day privilege escalation bug and a series of high‑impact Office and PowerShell vulnerabilities—users and organizations are urged to apply the patches without delay. Staying ahead of the threat landscape requires not only prompt update installation but also a comprehensive security posture that incorporates user awareness, network defenses, and advanced endpoint protection.

References

• Microsoft Security Response Center – CVE‑2025‑62221
• Microsoft Security Response Center – CVE‑2025‑64671
• SANS Internet Storm Center – Microsoft Patch Tuesday December 2025