A fresh flaw hides inside Windows 11’s January patch – this one halts startup entirely on impacted machines. Boot attempts collapse before the system can load.
Something odd showed up on the Ask Woody forums – a note pointing at Microsoft admitting there’s a problem. A few machines now hit a wall during startup, flashing “UNMOUNTABLE_BOOT_VOLUME.” This started creeping in after folks installed the Windows patch from January 13, 2026, along with those that followed. Reports remain small, yet clear enough for Redmond to confirm it’s real. The glitch ties directly to that month’s security rollouts. Not everyone sees it, but when it strikes, the system won’t start.
“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.”
- There’s a new bug in Windows 11’s January update
- Microsoft informs us that this one is causing boot failures based on a “limited number of reports”
- If affected, you’ll have to try a manual recovery, and Microsoft is now investigating this issue
Here’s what happens. Microsoft claims only a small number of computers face problems from this glitch. Trouble shows up in Windows 11 builds labeled 24H2 and 25H2. Few systems get affected, they say.
Here’s the downside: there’s a serious bug causing trouble. According to Microsoft, fixing it means stepping into the Windows Recovery Environment, otherwise known as WinRE. This space allows attempts at mending the operating system. Getting things working again happens only through this path.
Analysis: more bugs, more pain – and the obvious question
What does “limited” actually mean here? A few users running Windows 11 25H2 or 24H2 may run into this issue. Still, Microsoft gives no details about which versions – Home, Pro, or enterprise – are affected. The scope remains unclear.
Finding folks on Reddit – often a go-to spot for spotting hiccups with Windows upgrades – I stumbled upon one post where seven users each described getting stuck during startup after installing the newest patch
Truth is, there aren’t many confirmed cases out there just yet, still stories about problems keep popping up online. A few say Microsoft’s quick fix – KB5078127 – solves the startup trouble, yet that solution hasn’t been officially linked to these issues according to Windows Latest’s sources. That patch does handle several bugs making programs like Outlook stop working suddenly. Worth installing regardless, really. Even so, once you’ve loaded the January update without seeing start-up errors, chances are everything will stay fine.
People waiting on the January update because of earlier bugs might still want to hold back. This latest issue needs more digging by Microsoft – something already happening, per Neowin. A pause could make sense till things clear up.
One moment you’re updating your system, next thing – a full stop. Skipping a Windows 11 patch isn’t something I’d usually suggest, especially when protections are on the line. Yet here we are: reports of crashes so severe they outdo typical malware chaos. True? Maybe not exactly – still, the frustration feels real. You hold the final say, sure – the flaw appears uncommon – but rare doesn’t equal safe. That glitch might just find its way in after the January patch slips through.
Few updates have surfaced about the January bug said to disrupt sleep mode across certain older computers.