Stay ahead of critical vulnerabilities with our breakdown of this month's Microsoft security patches.
Microsoft concluded 2025 with its final Patch Tuesday release on December 9, delivering security fixes for 56 vulnerabilities across Windows, Office, Exchange Server and other critical components. This month's update is particularly significant as it addresses three zero-day vulnerabilities, including one actively exploited in the wild.
Release Date: December 9, 2025
Total CVEs Addressed: 56
Zero-Day Vulnerabilities: 3
Critical Severity Issues: 2
Actively Exploited: 1 (CVE-2025-62221)
This use-after-free vulnerability in the Windows Cloud Files Mini Filter Driver has been detected in active attacks, marking it as the most urgent patch in this month's release. The flaw allows attackers to elevate privileges on compromised systems, making it a critical component of multi-stage attack chains.
Severity: Important
CVSS Score: 7.0-7.8 (estimated)
Impact: Elevation of Privilege
Status: Exploited in the wild
Immediate Action Required: Organizations should prioritize deploying this patch immediately, as threat actors are already leveraging this vulnerability in active campaigns.
This command injection vulnerability in GitHub Copilot for JetBrains enables local remote code execution. While publicly disclosed, Microsoft assesses exploitation as "less likely."
Severity: Important
Impact: Remote Code Execution (Local)
Status: Publicly disclosed, not actively exploited
This vulnerability affects PowerShell through command injection, similar to the GitHub Copilot flaw. The December update includes enhanced security warnings for PowerShell 5.1's Invoke-WebRequest cmdlet to mitigate script execution risks.
Severity: Important
Impact: Remote Code Execution
Status: Publicly disclosed, not actively exploited
The December update addresses two critical remote code execution vulnerabilities in Microsoft Office, both rated critical due to their potential for arbitrary code execution via malicious documents. These vulnerabilities affect multiple Office applications including:
Organizations should exercise extreme caution when opening documents from untrusted sources, as attackers can weaponize these flaws through phishing campaigns and malicious email attachments.
The majority of patches address elevation of privilege flaws in Windows kernel drivers like Cloud Files Mini Filter Driver and Win32k, alongside remote code execution bugs in RRAS and ReFS. Key affected components include:
This month's updates impact a wide range of Microsoft products:
December marks the second Patch Tuesday following Windows 10's end-of-life on October 14, 2025. Organizations still running Windows 10 must be enrolled in the Extended Security Update (ESU) program to receive security updates.
Critical ESU Requirements:
Exploitation likelihood varies, with several vulnerabilities marked as "More Likely" or "Detected," urging immediate patching amid holiday slowdowns. Microsoft's exploitation assessment includes:
December Patch Tuesday presents unique challenges due to reduced operations during the Western holidays and New Year's Day. Microsoft announced that due to reduced operations during the Western holidays and New Year's Day, they will not release a non-security preview update in December 2025, though the monthly security update remains available as scheduled.
With year-end holidays approaching, organizations should automate patching to mitigate risks from the 1,100+ CVEs patched in 2025. This year has been marked by:
Beyond Patch Tuesday updates, organizations should implement defense-in-depth strategies:
Organizations should also plan for concurrent security updates from other vendors:
As we enter 2026, several developments warrant attention:
IT teams should be aware that Secure Boot certificates used by most Windows devices are set to expire starting in June 2026. Organizations should begin reviewing guidance and updating certificates well in advance.
The increasing integration of AI technologies into cybersecurity solutions will likely play a larger role in patch management and vulnerability detection throughout 2026.
Regular monthly servicing, including both security updates and non-security preview updates, will resume in January 2026.
December 2025's Patch Tuesday represents a critical security milestone as Microsoft addresses 56 vulnerabilities, including one actively exploited zero-day. The active exploitation of CVE-2025-62221 demands immediate attention, while the two critical Office RCE vulnerabilities pose significant risks through social engineering attacks.
Organizations must balance the urgency of these security updates with the operational challenges of holiday schedules. Automated patch management, thorough testing and prioritized deployment strategies are essential to maintaining security posture during this traditionally slower period.
As we close out a year that saw over 1,100 CVEs addressed by Microsoft, the December release serves as a reminder that cybersecurity threats don't take holidays. IT and security teams must remain vigilant and ensure these critical patches are deployed promptly to protect their organizations.
| CVE ID | Component | Type | Status | Priority |
|---|---|---|---|---|
| CVE-2025-62221 | Windows Cloud Files | EoP | EXPLOITED | CRITICAL |
| CVE-2025-64671 | GitHub Copilot | RCE | Public | High |
| CVE-2025-54100 | PowerShell | RCE | Public | High |
| Multiple | Microsoft Office | RCE | None | Critical |
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