Microsoft Patch Tuesday for January 2026

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1. Actively Exploited Zero-Day (CVE-2026-20805)

  • Impact: Attackers can read sensitive memory addresses, weakening ASLR and enabling exploit chaining.
  • Risk: High for environments running Windows Desktop Window Manager (DWM).
  • Action: Prioritize patching all Windows endpoints and servers immediately.

2. Secure Boot Certificate Expiration (CVE-2026-21265)

  • Impact: Expired certificates could allow Secure Boot bypass, undermining OS integrity.
  • Risk: Critical for enterprises relying on Secure Boot for compliance and device trust.
  • Action: Update Secure Boot certificates and validate boot chain integrity across all managed devices.

3. Legacy Driver Privilege Escalation (CVE-2023-31096)

  • Impact: Vulnerable modem drivers (agrsm.sys) can grant attackers elevated privileges.
  • Risk: High in environments with older hardware or legacy drivers still present.
  • Action: Remove deprecated drivers and apply patches to prevent privilege escalation.

4. Broader Vulnerability Landscape

  • 114 flaws total, including:
    • 57 Elevation of Privilege – Could enable lateral movement.
    • 22 Remote Code Execution – Direct compromise risk for servers and endpoints.
    • 22 Information Disclosure – Data leakage risk.
  • Critical services affected: Windows OS, Secure Boot, legacy components.

Enterprise Recommendations

  • Immediate Patch Deployment: Focus on zero-days and critical RCE/EoP vulnerabilities.
  • Asset Inventory Check: Identify systems with legacy drivers and Secure Boot dependencies.
  • Compliance Validation: Ensure patched systems meet regulatory and internal security baselines.
  • Threat Monitoring: Watch for exploit attempts targeting CVE-2026-20805 in telemetry.

Roadmap for Deployment


Phase 1: Immediate Action (Within 24–48 Hours)

Focus: Zero-day vulnerabilities and critical RCE/EoP flaws

  • Patch CVE-2026-20805 (DWM Info Disclosure)
    • Actively exploited; patch all Windows endpoints and servers.
  • Patch CVE-2026-21265 (Secure Boot Certificate Expiration)
    • Update Secure Boot certificates and validate boot chain integrity.
  • Patch CVE-2023-31096 (Legacy Modem Driver EoP)
    • Remove deprecated drivers and apply updates.
  • Critical Remote Code Execution vulnerabilities
    • Prioritize systems exposed to the internet (e.g., web servers, remote access gateways).

Phase 2: High-Risk Systems (Within 3–5 Days)

Focus: Elevation of Privilege and RCE vulnerabilities

  • Patch Windows Server roles (Domain Controllers, Exchange, SQL Servers).
  • Patch VDI environments and critical endpoints used by privileged users.
  • Validate Group Policy and Secure Boot enforcement across all devices.

Phase 3: Broad Deployment (Within 1–2 Weeks)

Focus: Remaining vulnerabilities and compliance hardening

  • Apply cumulative updates to all Windows 10/11 endpoints.
  • Patch non-critical servers and workstations.
  • Remove legacy components flagged in vulnerability scans.

Phase 4: Post-Patch Validation

  • Run vulnerability scans to confirm patch application.
  • Monitor telemetry for exploit attempts targeting CVE-2026-20805.
  • Update compliance dashboards to reflect patched systems.

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