January 2026 Microsoft Patch Tuesday: What’s New, What Broke & Why It Matters

Complete Security Update Breakdown + Expert Guidance from Secure Chain Technology Group

January 2026 was one of Microsoft’s most turbulent Patch Tuesday cycles in recent years — combining 114+ security fixes, multiple zero‑day vulnerabilities, active exploitation, and a rare double wave of emergency out‑of‑band (OOB) updates. Organisations worldwide faced instability, outages, and critical risk windows as flaws surfaced immediately after deployment.

This article provides a complete, SEO‑optimised, AI‑search‑ready breakdown of:

• What was included in the January 2026 Patch Tuesday release
• Zero‑day vulnerabilities and critical CVEs
• Known issues and emergency updates
• The pros & cons of installing these updates
• How Secure Chain Technology Group protects your estate during chaotic patch cycles

What Was Included in the January 2026 Microsoft Security Updates

114–115 Security Vulnerabilities Fixed

Microsoft addressed 114+ vulnerabilities across Windows, Office, SharePoint, Hyper‑V, LSASS, and Microsoft services. Breakdown:

• 57 Elevation of Privilege vulnerabilities
• 22 Remote Code Execution flaws
• 22 Information Disclosure vulnerabilities
• 3 Security Feature Bypass vulnerabilities
• 5 Spoofing vulnerabilities

Three Zero‑Day Vulnerabilities (One Actively Exploited)

CVE‑2026‑20805 — Desktop Window Manager (Actively Exploited Zero‑Day)

• Enables attackers to read sensitive memory addresses
• Can help bypass ASLR, enabling exploit chains
• Affects Windows 10, 11 & Server editions

CVE‑2026‑21265 — Secure Boot Certificate Expiration

• Publicly disclosed
• Impacts OS boot integrity from mid‑2026 onwards
• Failure to update could cause system boot failures

CVE‑2023‑31096 — Legacy Agere Soft Modem Driver Zero‑Day

• Allows SYSTEM‑level privilege escalation
• Microsoft removed vulnerable drivers entirely in the update

Office Zero‑Day (CVE‑2026‑21509)

• Actively exploited
• Allows attackers to bypass OLE security checks via malicious Office files
• Requires user to open the malicious document

Known Issues After Installing the January 2026 Updates

❌ Boot Failures: UNMOUNTABLE_BOOT_VOLUME (KB5074109)

• Affected Windows 11 24H2 and 25H2
• Systems entered an “improper state” from December 2025 update failures
• Required full manual recovery

❌ Outlook Classic Freezing, PST Issues, Files Redownloading

• Outlook crashed when PST files were synced via OneDrive / Dropbox
• Many third‑party applications accessing cloud‑stored files also froze

❌ Remote Desktop Sign‑In Failures

• Users unable to authenticate in Azure‑based and on‑prem RDP sessions

❌ Sleep Mode, Shutdown, File Explorer Issues

• Sleep mode (S3) stopped working on older devices
• Shutdown and hibernation became unreliable
• desktop.ini and customisation behaviours broke

❌ Cascading Failures From Multiple Emergency Patches

Patch‑break‑patch behaviour occurred:

1. January 13 Patch Tuesday released
2. January 17 First OOB fix released — created new bugs
3. January 24 Second OOB fix (KB5078127) released to stabilise systems
   [techrepublic.com]

Emergency Out‑of‑Band Updates Released

KB5077744 — Emergency Fix #1 (17 January 2026)

• Attempted to fix shutdown and Remote Desktop issues
• Introduced new file system & cloud‑sync problems

KB5078127 — Emergency Fix #2 (24 January 2026)

• Mandatory emergency update
• Restored Outlook Classic POP/PST functionality
• Fixed unresponsive applications using cloud storage

Pros &  Cons of Installing the January 2026 Updates

Pros (Why You Should Install Them)

1. Critical Security Protection

• Several vulnerabilities are under active exploitation
• Zero‑day Office and DWM flaws allow targeted attacks

2. Maintaining Compliance (ISO, CE+, NCSC, GDPR)

Regulators expect businesses to patch within defined windows — these updates contain high‑severity CVEs affecting:

• Authentication (LSASS)
• Secure Boot
• Office document handling

3. Preventing Privilege Escalation & Lateral Movement

Updates close multiple escalation paths attackers use to gain SYSTEM‑level access.

✘ Cons (The Risks & Pain Points)

1. Potential for System Instability

• Boot failures, RDP authentication failures, Outlook crashes
• Cloud‑synced applications becoming unusable

2. Operational Disruption

Unexpected OOB updates can force out‑of‑cycle maintenance windows.

3. Increased Administrative Overhead

Teams must test rollback plans, validate dependencies, and monitor cascading update issues.

🔧 How Secure Chain Technology Group Helps You Stay Secure & Stable

Secure Chain Technology Group supports structured patching and risk‑based remediation. Here’s how we help:

1. Fully Managed Patch Management (VMaaS & PMaaS)

We deliver:

• Automated identification, testing & deployment
• Zero‑downtime patching windows
• Compliance‑ready reporting & audit trails

2. Vulnerability Prioritisation & Remediation Tracking

Process & Tracker workflows ensure:

• Full lifecycle tracking of every CVE
• Business‑unit‑specific asset grouping
• Rollback planning and remediation ownership

3. Emergency Patch Response

During chaotic update cycles like January 2026, Secure Chain provides:

• Rapid impact assessments
• Deployment advice for emergency OOB updates
• Mitigation plans when patches cause new issues

4. Strategic Advisory for Zero‑Day Mitigation

Including:

• Hardening baselines
• ASR rule deployment
• Office macro & OLE protections
• User‑focused awareness guidance

5. Alignment with Cyber Essentials, ISO 27001 & NCSC Best Practice

Patch windows, unsupported hardware identification, and remediation escalation workflows all support CE+ and ISO audits.