🎯 December 2025 Patch Tuesday: What’s Inside

On December 9, 2025, Microsoft rolled out its December Patch Tuesday, which fixed 57 security flaws — including three zero-day vulnerabilities (one of them actively exploited) and several other critical issues.

Here’s a breakdown of the types of vulnerabilities addressed this month:

  • 28 Elevation-of-Privilege vulnerabilities

  • 19 Remote Code Execution (RCE) vulnerabilities

  • 4 Information Disclosure vulnerabilities

  • 3 Denial of Service (DoS) vulnerabilities

  • 2 Spoofing vulnerabilities

Importantly, this tally doesn’t include separately released patches for components like Microsoft Edge (15 flaws) or Mariner, which were addressed earlier this month.

🔐 Three Zero-Days Addressed — Including One Under Active Attack

✅ Actively Exploited: CVE-2025-62221

  • A use-after-free vulnerability in the Windows Cloud Files Mini Filter Driver allows local attackers with limited access to escalate privileges — potentially reaching full SYSTEM-level control.

  • Because it’s already being exploited “in the wild,” patching this is a top priority.

💻 Publicly Disclosed Zero-Days — CVE-2025-64671 & CVE-2025-54100

  • CVE-2025-64671 affects GitHub Copilot for JetBrains. A command-injection flaw (via cross-prompt injection) can allow unauthorized code execution in developer environments that use Copilot + JetBrains IDEs.

  • CVE-2025-54100 affects PowerShell. Under certain conditions (e.g. using Invoke-WebRequest), embedded scripts from downloaded web content could be executed — risking remote code execution.

Although these two weren’t (to public knowledge) exploited in the wild yet, their public disclosure increases the risk that attackers could reverse-engineer exploits quickly — so they should still be high on the patch list.

⚠️ Other Critical Vulnerabilities: RCE & Privilege Escalation Across Microsoft Products

Beyond the zero-days, this month’s updates also patch multiple critical Remote Code Execution (RCE) vulnerabilities — including issues in core Windows components, Office applications (Word, Excel, Outlook), and services like Routing and Remote Access.

These kinds of vulnerabilities are especially dangerous because, if exploited, they can allow attackers to run arbitrary code — potentially taking over systems, deploying malware or ransomware, or moving laterally across networks.

Given the range — from local privilege escalations to remote code execution — the update spans many attack vectors and requires broad patch deployment across desktops, servers, and developer workstations.

🛡️ What You (or Your Org) Should Do — ASAP

  1. Patch immediately: Especially on systems exposed to risk — desktops, servers, and workstations. The zero-day CVE-2025-62221 is already exploited; delay means risk.

  2. Prioritize critical systems & dev environments: If you use tools like GitHub Copilot + JetBrains IDEs, or rely heavily on PowerShell automation, ensure those environments are updated first.

  3. Reboot after patching: Many of the updates affect core Windows components — full system reboot ensures patches load properly.

  4. Audit scripts & permissions: For instance, review Invoke-WebRequest calls in PowerShell scripts, and strictly limit privilege levels for users — especially on shared or sensitive systems.

  5. Stay alert to follow-on updates: Because some fixes may have side-effects (e.g. compatibility issues), monitor for additional patches or hotfixes, and verify system stability after updates.

🔎 Why This Patch Tuesday Matters — And What It Says About the Current Threat Landscape

  • The fact that one zero-day is already under active exploitation demonstrates just how aggressively attackers are pushing to weaponize Windows internals — especially components like file-system drivers.

  • The inclusion of a vulnerability in a developer-focused tool (GitHub Copilot for JetBrains) highlights a growing trend: attackers targeting development environments & supply chains, not just end-user desktops.

  • With 57 flaws patched at once — across privilege escalation, remote execution, privilege escalation, information leaks, and spoofing — it’s not just a “one-or-two bug fix” update. It underscores how complex and multi-vector modern Windows threats have become.

  • For organizations, this means patch management and proactive vulnerability management are no longer optional — they are foundational security hygiene.

In short: this December’s Patch Tuesday isn’t just “important” — it’s urgent.