vulnerabilities

December Patch Tuesday Fixes 3 Actively Exploited Zero-Days

breachwire TeamDec 11, 20255 min read

Executive Summary

Microsoft’s December Patch Tuesday has rolled out security updates targeting 57 vulnerabilities, including three critical zero-days—one of which is currently under active exploitation. These flaws present elevated risk to enterprise environments, making this a top priority for security leaders and operations teams. This month’s daily briefing reveals how threat actors are hijacking Windows systems using privilege escalation and remote execution techniques, emphasizing the need for immediate patch validation and PowerShell scrutiny.

CISOs must act swiftly to ensure patch compliance across Windows 10, 11, and Server platforms, while also mitigating the elevated PowerShell execution risks tied to recent attack campaigns.

What Happened

On December 10, Microsoft published its final Patch Tuesday of 2025, fixing 57 CVEs across the Windows ecosystem. Among these, three vulnerabilities stand out for their severity and risk posture:

CVE-2025-62221 — an actively exploited privilege escalation flaw in the Windows Cloud Files Mini Filter Driver.
CVE-2025-64671 — a remote code execution (RCE) vulnerability impacting GitHub Copilot for JetBrains.
CVE-2025-54100 — a code execution flaw in Windows PowerShell, linked to exploitation methods like ClickFix.

Notably, PowerShell security received specific attention: Microsoft updated its behavior when using Invoke-WebRequest to issue warnings when fetched web content lacks safe parameters—potentially exposing scripts to unintended execution.

While Windows 11 users receive both feature updates and security patches, Windows 10 is now on a strictly security-patch-only lifecycle, leaving these fixes as critical for maintaining minimal security baselines for aging assets.

Why This Matters for CISOs

On the surface, this appears to be another routine Patch Tuesday. But the presence of an actively exploited local privilege escalation bug (CVE-2025-62221) immediately elevates urgency. If left unaddressed, attackers can use this flaw to elevate privileges on compromised systems—potentially chaining it with phishing payloads or lateral movement tactics.

The implications include:

Loss of endpoint visibility: Escalated privileges can be used to disable EDR tooling.
Supply chain compromise risk: The GitHub Copilot RCE vulnerability (CVE-2025-64671) can be leveraged during CI/CD operations.
Script-based execution vectors: PowerShell web-fetching flaws reflect persistent abuse trends, including weaponized automation and trusted pipeline abuse.

CISOs must prioritize visibility into patch deployment status, especially for assets exposed to development tools and PowerShell scripting activities. These represent threat actors’ preferred lateral surfaces.

Threat & Risk Analysis

Attack Vectors

CVE-2025-62221: Local users can exploit the Cloud Files Mini Filter Driver to gain SYSTEM-level access. Likely seen in post-compromise privilege escalation chains.
CVE-2025-64671: Malicious code injection via Copilot/JetBrains IDE interactions—ideal for developer-targeted attacks and CI/CD backdoors.
CVE-2025-54100: Abuse of unsanitized PowerShell scripts via Invoke-WebRequest mirrors techniques used in campaigns like ClickFix.

Exposure Scenarios

Legacy or unsupported Windows 10 devices that remain unpatched.
Developer endpoints using vulnerable plugins or AI coding assistants.
Automation pipelines fetching unsigned or unvalidated scripts over HTTP/S.

Supply Chain Relevance

Development tools like GitHub Copilot and JetBrains integrations are deeply embedded in DevOps workflows. CVE‑2025‑64671 adds yet another proof point that IDEs and helper utilities can serve as beachheads into source repositories or build systems.

Attacker Motivations

Privilege escalation for ransomware staging (CVE-2025-62221).
Backdooring automated code pipelines (CVE-2025-64671).
Script-based lateral movement and cloud persistence (CVE-2025-54100).

Potential Enterprise Impact

Widespread privilege abuse in hybrid Windows fleets.
Integrity compromise within software delivery ecosystems.
Evasion of security monitoring via trusted PowerShell behaviors.

For more on protecting against these exploitation trends, refer to our guide on comprehensive patch management strategy and ensure your SOC incorporates daily cyber threat briefings.

MITRE ATT&CK Mapping

T1068 — Exploitation for Privilege Escalation
Used to elevate from user to SYSTEM via CVE-2025-62221.
T1059.001 — PowerShell
Exploitation of Invoke-WebRequest without parameter sanitization.
T1609 — Container Administration Command
Borderline risk if PowerShell misuse crosses into container payloads.
T1552 — Unsecured Credentials
Post-privilege escalation reconnaissance to exfiltrate secrets.
T1047 — Windows Management Instrumentation
Common lateral tactic post-escalation using SYSTEM powers.
T1053 — Scheduled Task/Job
Likely used to persist malicious scripts in PowerShell attack chains.

Key Implications for Enterprise Security

Elevated risk from unpatched development tools or legacy Windows hosts.
PowerShell scripting risks are reemerging through new abuse patterns.
Enterprises with CI/CD ecosystems must verify IDE security posture.
Attack chains may bridge privilege escalation with automation abuse.

Recommended Defenses & Actions

Immediate (0–24h)

Deploy all Microsoft December patches across Windows 10, 11, and Server.
Alert SOC teams to monitor for Invoke-WebRequest behaviors lacking proper flags.
Validate GitHub Copilot integrations for RCE mitigation status.

Short Term (1–7 days)

Audit Privileged Access Workstations for CVE-2025-62221 exposure.
Enforce strict script-origin policies in automation pipelines.
Perform endpoint scans for unauthorized elevation events or ATS entries.

Strategic (30 days)

Transition DevSecOps practices to include vendor plugin audit routines.
Isolate developer endpoints from Internet-exposed workloads.
Integrate PowerShell activity monitoring into SIEM baselines.

Conclusion

This month’s Patch Tuesday underscores the persistent evolution in attacker behavior—combining privilege escalation, IDE abuse, and PowerShell vectors. For CISOs, the December daily threat updates highlight how even “routine” patches may cloak highly strategic threat capabilities. Proactive defense demands more than patching—it requires behavioral detection, workflow hardening, and daily briefing integration into the core cyber operations model.

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