As part of its December 2025 Patch Tuesday release—the final security update of the year—Microsoft addressed 56 vulnerabilities affecting Windows and related components. Notably, one of these flaws is confirmed to be actively exploited in the wild.

Vulnerability Overview

  • Total vulnerabilities patched: 56
  • Severity ratings: 3 Critical, 53 Important
  • Publicly disclosed prior to patching: 2
  • Vulnerability categories:
    • 29 elevation-of-privilege
    • 18 remote code execution
    • 4 information disclosure
    • 3 denial-of-service
    • 2 spoofing issues

Patch Activity in 2025

Across 2025, Microsoft remediated 1,275 CVEs, making it the second year in a row—and only the third time since the introduction of Patch Tuesday—that annual patches exceeded the 1,000-vulnerability threshold.

Additional Microsoft Edge Fixes

Outside the main Patch Tuesday cycle, Microsoft also corrected 17 vulnerabilities in its Chromium-based Edge browser since November 2025. Among them was a spoofing flaw in Edge for iOS (CVE-2025-62223, CVSS 4.3).

Actively Exploited Zero-Day: CVE-2025-62221

Issue Details:
CVE-2025-62221 is a use-after-free vulnerability in the Windows Cloud Files Mini Filter Driver, rated CVSS 7.8. Exploitation enables an authenticated local attacker to escalate privileges and obtain SYSTEM-level access.

Attack Scenario:
While technical exploitation details remain limited, attackers must first achieve initial access—such as through phishing or a browser-based exploit—before leveraging this flaw. Security researchers indicate the vulnerability can be chained with initial compromise techniques to fully take over affected systems. Once elevated, attackers could install kernel components or abuse signed drivers to evade defenses and establish persistence, potentially enabling broader domain compromise.

Regulatory Response:
Given evidence of active exploitation, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, mandating remediation by December 30, 2025 for federal agencies.

Other Significant Vulnerabilities Addressed

Microsoft also patched two additional publicly disclosed zero-day flaws:

  1. CVE-2025-54100 (CVSS 7.8): A Windows PowerShell command injection vulnerability allowing local, unauthorized code execution.
  2. CVE-2025-64671 (CVSS 8.4): A command injection issue in GitHub Copilot for JetBrains, enabling local code execution.

The “IDEsaster” Vulnerability Class

CVE-2025-64671 is part of a broader group of vulnerabilities collectively referred to as “IDEsaster.” These issues arise from the integration of agentic AI capabilities into development environments, which introduces new attack surfaces—particularly prompt injection risks. Attackers can manipulate AI prompts, including via file contents or external data sources, to coerce IDE-integrated agents into executing commands or leaking sensitive information. Some attacks involve cross-prompt injection, where the AI modifies its own instructions based on untrusted input.

Impacted Tools:
Similar weaknesses were identified across several AI-enabled IDEs and tools, including Kiro.dev, Cursor, JetBrains Junie, Gemini CLI, Windsurf, and Roo Code. GitHub Copilot for Visual Studio Code was also affected; however, Microsoft classified it as medium severity and did not assign a CVE.

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