Microsoft investigates Windows 11 boot failures after January updates

BleepingComputer

January 25, 2026 at 1:20 PM

Overview

Microsoft is looking into issues with some Windows 11 devices that are failing to boot after users installed the January 2026 Patch Tuesday security updates. Affected users are encountering 'UNMOUNTABLE_BOOT_VOLUME' errors, which prevent their systems from starting up properly. This situation could disrupt the workflow of many individuals and organizations that rely on Windows 11 for daily operations. Microsoft has not yet provided a specific fix or workaround for the problem, leaving users uncertain about how to resolve the issue. The investigation is ongoing as the company seeks to identify the root cause of the boot failures and implement a solution.

Key Takeaways

Affected Systems: Windows 11 devices
Timeline: Ongoing since January 2026

Original Article Summary

Microsoft is investigating reports that some Windows 11 devices are failing to boot with "UNMOUNTABLE_BOOT_VOLUME" errors after installing the January 2026 Patch Tuesday security updates. [...]

Impact

Windows 11 devices

Exploitation Status

The exploitation status is currently unknown. Monitor vendor advisories and security bulletins for updates.

Timeline

Ongoing since January 2026

Remediation

Not specified

Additional Information

This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.

Related Topics: This incident relates to Windows, Microsoft, Patch.

Read Original Article

Related Coverage

ShadowPad Malware Actively Exploits WSUS Vulnerability for Full System Access

The Hacker News

The ShadowPad malware is exploiting a recently patched vulnerability in Microsoft Windows Server Update Services (WSUS), identified as CVE-2025-59287, allowing attackers to gain full system access. This exploitation highlights the critical need for organizations to promptly apply security updates to vulnerable systems to prevent unauthorized access.

Nov 24, 2025

⚡ Weekly Recap: Fortinet Exploit, Chrome 0-Day, BadIIS Malware, Record DDoS, SaaS Breach & More

The Hacker News

This week, significant cybersecurity threats emerged as hackers exploited new 0-day vulnerabilities in Fortinet and Chrome, infiltrating supply chains and SaaS tools. The rapid response from major companies like Microsoft, Salesforce, and Google highlights the severity of these attacks and the ongoing challenges in securing trusted applications and software updates.

Nov 24, 2025

Microsoft Highlights Security Risks Introduced by New Agentic AI Feature

SecurityWeek

Microsoft has raised concerns about the security risks associated with its new Agentic AI feature, highlighting the potential for AI agents to engage in malicious activities like data exfiltration and malware installation if not properly secured. This underscores the critical need for robust security controls to mitigate these risks.

Nov 24, 2025

ToddyCat’s New Hacking Tools Steal Outlook Emails and Microsoft 365 Access Tokens

The Hacker News

ToddyCat, a threat actor, has developed a new tool called TCSectorCopy to steal Outlook emails and Microsoft 365 access tokens by exploiting the OAuth 2.0 authorization protocol through users' browsers. This poses a significant threat to corporate email security, as it allows unauthorized access to sensitive information outside the compromised infrastructure.

Nov 25, 2025

Microsoft: Security keys may prompt for PIN after recent updates

BleepingComputer

Microsoft has alerted users that FIDO2 security keys may require a PIN for sign-in following recent Windows updates since September 2025. This change could affect user experience and security practices, particularly for those relying on these security keys for authentication.

Nov 26, 2025

Microsoft to secure Entra ID sign-ins from script injection attacks

BleepingComputer

Microsoft is set to enhance the security of its Entra ID authentication system to protect against external script injection attacks starting in mid-to-late October 2026. This improvement aims to mitigate potential vulnerabilities that could be exploited by attackers to compromise user sign-ins.

Nov 26, 2025