Microsoft Patch Tuesday December 2025 – 56 Security Flaws

The latest Microsoft Patch Tuesday has rolled out 56 security fixes that span Windows, Office, and even the GitHub Copilot Plugin for JetBrains. As always, the update batch includes a mix of zero‑day exploits, privilege escalation bugs, and remote code execution vulnerabilities that could threaten enterprise and personal environments alike.

What Happens on Microsoft Patch Tuesday?

Microsoft’s Patch Tuesday is the company’s quarterly event where security patches are released for its software ecosystem. The focus keyword microsoft patch tuesday appears right at the start, ensuring both search engines and readers know the article’s core topic. The patch cycle is a predictable rhythm that allows IT teams to plan testing, deployment, and monitoring around a known release window.

Key Statistics for December 2025

In 2025, Microsoft patched 1,129 vulnerabilities, an 11.9% rise from the previous year. The December batch is the final one of the year, and it includes a zero‑day CVE‑2025‑62221 that is already being exploited in the wild. The overall mix of critical, high, medium, and low severity patches reflects the company’s ongoing effort to shore up weaknesses across its product portfolio.

Zero‑Day CVE‑2025‑62221: A Privilege Escalation Threat

At the heart of this month’s releases is CVE‑2025‑62221, a privilege escalation vulnerability that targets the Windows Cloud Files Mini Filter Driver. This driver is integral to cloud file services such as OneDrive, Google Drive, and iCloud. Even if none of these applications are installed, the driver remains part of the core Windows operating system, making it a high-value target for attackers.

The flaw allows an attacker to elevate privileges by manipulating the driver’s handling of certain file system calls. A successful exploitation could enable a user to gain SYSTEM level access, paving the way for broader lateral movement or data exfiltration. Microsoft has rated this vulnerability as “critical,” and it is already being actively exploited in several high‑profile incidents.

Office and Outlook Vulnerabilities Exploited via Preview Pane

Three Office-related bugs made the critical list:

• CVE‑2025‑62554 – Exploitable by opening a malicious email in the Outlook preview pane.
• CVE‑2025‑62557 – Similar vector, affecting Word and Excel rendering.
• CVE‑2025‑62562 – Targets Outlook’s rendering engine; the preview pane is not a direct attack vector, but the bug can be triggered by viewing a specially crafted attachment.

These vulnerabilities highlight the continued risk posed by email clients that render potentially malicious content. Even in a controlled environment, the preview pane can inadvertently execute code, underscoring the need for up‑to‑date security patches.

Privileged Escalation Bugs Across Windows Components

While only a handful of bugs are labeled critical, Microsoft identified several non‑critical yet high‑risk privilege escalation flaws that are likely to be exploited. These include:

1. CVE‑2025‑62458 – A Win32k kernel driver issue that could allow local attackers to elevate privileges.
2. CVE‑2025‑62470 – A Windows Common Log File System Driver vulnerability that may lead to privilege escalation.
3. CVE‑2025‑62472 – Remote Access Connection Manager flaw that could be leveraged for privilege escalation.
4. CVE‑2025‑59516 – A Windows Storage VSP Driver bug with potential privilege escalation.
5. CVE‑2025‑59517 – Another Windows Storage VSP Driver vulnerability with similar impact.

These components are foundational to Windows’ operation, and the potential for exploitation makes them a priority for rapid patching.

Remote Code Execution in the GitHub Copilot Plugin

One of the most unexpected findings this month is CVE‑2025‑64671, a remote code execution flaw in the GitHub Copilot Plugin for JetBrains. The plugin, an AI‑based coding assistant, is used by developers across the globe. The vulnerability allows an attacker to trick the large language model into executing arbitrary commands by manipulating the “auto‑approve” feature. This bug is part of a larger “IDEsaster” wave of vulnerabilities that threaten integrated development environments and AI coding tools.

Security researcher Ari Marzuk has documented more than 30 related flaws across platforms like Cursor, Windsurf, Gemini CLI, and Claude Code. The breadth of these vulnerabilities signals a systemic issue in how AI models interface with code execution environments. Developers and organizations should immediately update the Copilot plugin and consider disabling auto‑approve until a patch is released.

PowerShell Remote Code Execution Bug

CVE‑2025‑54100 is a remote code execution vulnerability in Windows PowerShell affecting Server 2008 and newer. An unauthenticated attacker can run code in the context of the user, potentially bypassing security controls. PowerShell is a powerful automation tool, but its misuse can have catastrophic effects. Microsoft recommends applying the patch and reviewing execution policies on all servers that use PowerShell.

Why These Patches Matter for Your Organization

Security updates are not just a formality; they are the first line of defense against emerging threats. The December 2025 patch set includes zero‑days and high‑severity bugs that have already been exploited in the wild. If your environment runs Windows 10 or later, Office 365, or any of the affected components, the risk of compromise is real and immediate.

IT teams should:

• Verify that all endpoints are running the latest updates from the Microsoft Security Response Center.
• Test patches in a staging environment before wide deployment to avoid compatibility issues.
• Review the SANS Internet Storm Center roundup for detailed technical notes on each vulnerability.
• Implement least‑privilege principles and restrict the use of PowerShell on critical servers.
• Educate users about the dangers of opening unknown attachments or clicking on suspicious links, especially when preview panes are involved.

Practical Example: Mitigating the CVE‑2025‑62221 Exploit

Consider a corporate environment where Windows 10 machines are used for sensitive data handling. An attacker could craft a malicious file that exploits the Windows Cloud Files Mini Filter Driver, elevating a user’s privileges to SYSTEM. The attacker could then access encrypted data or install persistence mechanisms.

To mitigate:

1. Apply the patch as soon as it is available.
2. Disable the Cloud Files Mini Filter Driver on machines that do not require cloud file synchronization.
3. Implement endpoint detection and response (EDR) to monitor for anomalous file system activity.
4. Use application whitelisting to prevent unauthorized executables from running.

Staying Ahead of Future Threats

Patch management is only part of a comprehensive security strategy. Organizations should also:

• Regularly audit their software inventory to identify outdated components.
• Employ threat intelligence feeds to stay informed about new CVEs and exploit trends.
• Use sandboxing or virtual environments to test new software before deployment.
• Leverage Microsoft’s Advanced Threat Protection suite to detect and block exploitation attempts.

Conclusion

The December 2025 Microsoft Patch Tuesday delivers a broad set of security fixes that address both well‑known and emergent vulnerabilities. From a zero‑day privilege escalation flaw in Windows to a remote code execution bug in GitHub Copilot, the patches underscore the importance of timely updates. IT professionals must prioritize patch deployment, monitor for signs of compromise, and maintain a culture of security awareness to protect their assets against evolving threats.

References

• Microsoft Security Response Center
• SANS Internet Storm Center – Microsoft Patch Tuesday December 2025
• IDEsaster – Ari Marzuk’s Analysis of IDE Vulnerabilities