Microsoft has confirmed that some users might find their PC unable to boot after installing the January 2026 security update released on January 13. This is on top of the plethora of other issues that have been reported since Microsoft's disastrous Patch Tuesday updates arrived.
So far, the company has released two emergency out-of-band updates for Windows 11 to address major bugs that were introduced with this month's security updates, but this latest issue that is causing PCs to fail to boot has not yet been addressed.
"Microsoft has received a limited number of reports of an issue in which devices are failing to boot with stop code “UNMOUNTABLE_BOOT_VOLUME”, after installing the January 2026 Windows security update released January 13, 2026, and later updates," the company has confirmed in an online bulletin (via AskWoody.) "Affected devices show a black screen with the message “Your device ran into a problem and needs a restart. You can restart.” At this stage, the device cannot complete startup and requires manual recovery steps."
Microsoft says this issue is likely to impact users running Windows 11 version 24H2 and 25H2 on physical machines, and that it is exploring potential fixes and workarounds. In the meantime, if you do encounter this problem, you will need to manually recover your PC by entering the Windows Recovery Environment and uninstalling the latest January 2026 security patch.
It's unclear how common this issue is, as most users have not reported their PC unable to boot. The company says it has received a limited number of reports, but has not provided an explanation as to what is causing the unbootable state, or whether it can be avoided.
This is the latest in a long line of issues that were introduced with this month's Patch Tuesday updates. First, users reported that PCs running version 23H2 were unable to shutdown or hibernate, and PCs running version 24H2 and 25H2 were unable to sign-in when using Remote Desktop.
A few days later, reports came in confirming an issue that rendered cloud-backed apps like Outlook, Dropbox, and OneDrive inoperable, forcing Microsoft to issue two emergency updates to address these showstopping bugs. Now, with reports that some PCs are unable to boot, it's likely the company will need to issue a third out of band update to fix this problem too.
It's unclear why January's security update for Windows 11 has been so disastrous. Whatever the reason, Microsoft needs to step back and reevaluate how it developers Windows, as the current quality bar might be at the lowest it's ever been.
via Neowin
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