- There’s a new bug in Windows 11 January Update
- Microsoft tells us that it causes boot failures based on a “limited number of reports”
- If you are affected, you will need to try a manual recovery, and Microsoft is currently investigating this issue.
Windows 11 has another serious bug hidden in the January update, and it’s a roadblock that means affected PCs fail to boot.
Neowin reports that Microsoft acknowledged the bug with a post reported via the Ask Woody forums: “Microsoft has received a limited number of reports of an issue where devices fail to boot with the stop code ‘UNMOUNTABLE_BOOT_VOLUME’, after installing the Windows January 2026 Security Update, released on January 13, 2026, and later updates.
“Affected devices display a black screen with the message “Your device has encountered a problem and needs a restart. You can restart.” At this point, the device cannot complete startup and requires manual recovery steps.”
So the good news is that we are told that the impact is limited here, so few PCs are affected by the bug according to Microsoft. The company said the issues affected Windows 11 versions 24H2 and 25H2.
The less good news is that this is a nasty bug and, as Microsoft notes, you will have to do a manual recovery, that is, use the Windows Recovery Environment (WinRE). This can be used to try to repair the system, returning it to a functional state.
Analysis: even more bugs – and an obvious question
The question in this case is: how limited is the term “limited”? This suggests that a small number of people running Windows 11 25H2 and 24H2 are affected, although Microsoft doesn’t specify which versions of the operating system might be at risk here (in terms of Windows 11 Home or Pro, or Enterprise editions).
While searching Reddit, which is the most likely place to find (relatively reliable) reports of problems with Windows Updates, I came across this thread with seven separate complaints about boot failures caused by this latest Windows update.
One Redditor notes: “Can confirm. My PC actually didn’t boot. Recovery completely corrupted the startup drive and required a complete reformat and reinstall.” Another said he was getting a “disk read error” and a repair operation (via the recovery environment) did not resolve this issue. Another report states that a System Restore fixed their PC’s failure to boot, thankfully, so not everyone here is hitting a brick wall trying to recover their machine. (Note that these are primarily consumer computers – as opposed to business computers).
Now, I don’t see any other reports about this, but this update certainly ended badly for some people, based on the (anecdotal) complaints going around. Some also claim that the new emergency patch released by Microsoft – KB5078127 – fixes this failed boot issue, but that is not among the resolutions claimed here, based on what Windows Latest has heard from Microsoft. This emergency patch, however, fixes various gremlins causing apps to crash in Windows 11, including Outlook – and it’s obviously worth applying anyway. However, if you’ve already installed the January update and haven’t experienced a boot failure, you’re in the clear anyway.
However, those who have delayed the January update due to the various reported bugs may want to stay away for a while until Microsoft investigates this new issue in more detail (an ongoing process according to Neowin).
I wouldn’t normally recommend not installing a Windows 11 update – due to the lack of security patches applied to it – but in this case, as one Reddit user said, the damage caused to their PC by the update was worse than any virus. (Unlikely, actually – but you get the gist). Obviously, it’s up to you, and it seems the bug is rare – but that doesn’t mean it’s impossible for it to happen if you install the January update.
There’s still no news on the January update issue that reportedly torpedoed sleep mode on some (older) PCs.
The best laptops for every budget
Follow TechRadar on Google News And add us as your favorite source to get our news, reviews and expert opinions in your feeds. Make sure to click the Follow button!
And of course you can also follow TechRadar on YouTube And TikTok for news, reviews, unboxings in video form and receive regular updates from us on WhatsApp Also.
