Some PCs can't boot after latest Windows 11 security update, no fix in sight —mostly affects 24H2 and 25H2 versions

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This is one of the worst Windows security update bugs in recent memory.

Windows 11
(Image credit: Microsoft)

A few Windows 11 users have been affected by a bug from the latest Windows 11 security update, which resulted in their PCs refusing to turn on. According to an AskWoody forum post, there were reports that some devices encountered an “UNMOUNTABLE_BOOT_VOLUME” error after installing the January 2026 Windows security update. The affected computers came up with a black screen and a message that says “Your device ran into a problem and needs a restart. You can restart.”\

This isn’t the first issue that came out of Microsoft’s latest Windows security update, with some PCs refusing to shut down or hibernate, and another bug resulting in Cloud-based apps, like Outlook, OneDrive, and Dropbox, not working, as reported by Windows Central. The company has since released emergency updates to address these problems, but it seems that there is no fix for the unbootable error just yet. This is also the most catastrophic error yet, and the only workaround for this is to enter the Windows Recovery Environment and uninstall the latest security patch.

These security updates are supposed to keep Windows users secure, but it seems that they’re causing more harm than good at the moment. This also isn’t the first time that an update wreaked havoc on the popular operating system, with the August 2025 security update breaking recovery tools on both Windows 10 and 11. Another security update in October brought another issue, with USB keyboards and mice not working in Windows Recovery Environment, meaning users cannot actually do anything to troubleshoot their PC.

It’s unclear what caused the latest issue, and we’re still waiting on Microsoft to release an emergency update that will fix the problem. However, this is probably easier said than done, especially given that millions of PCs with a nearly infinite number of different hardware configurations out there have Windows 11 installed. But even if only a small number of Windows 11 users are affected by this catastrophic error, it’s still an issue that needs to be addressed quickly.

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Jowi Morales
Jowi Morales
Contributing Writer

Jowi Morales is a tech enthusiast with years of experience working in the industry. He’s been writing with several tech publications since 2021, where he’s been interested in tech hardware and consumer electronics.

24 Comments Comment from the forums
  • -Fran-
    Shocking! Shocking I tell you!

    Well, not so shocking.
    And then Satya doesn't want the "Microslop" name, when they prove over and over how sloppy they are.

    Heh.

    Regards.
    Reply
  • Jabberwocky79
    Well, that's just lovely, seeing as how I work from home and the usage of my PC is my basis for income. Guess I'll be postponing this update for as long as possible.
    Reply
  • Notton
    "mostly affects 24H2 and 25H2"
    Is it even possible to stick to 23H2 or older these days?
    Reply
  • mikeebb
    I can (dual-)boot into Linux Mint on the desktop. If I run into this kind of problem with the Windows side (which so far I haven't fingers crossed, though only the second of the "out of band" updates was actually applied), can I do anything from the Linux side to wake Windows back up again? Probably not (and getting into WRE directly is always a pain - have to do a bunch of internet searching from my phone or the Linux side on those rare occasions to remind me of the procedure), but thought I'd ask anyway.

    Oh, and what's with nearly all recent (since maybe fall 2025) Windows Updates requiring 2 restarts on the desktop (originally upgraded from Win10, unlike my laptop)? Laptop usually does it with one restart. It's a minor annoyance, since I have to sit there through the first update segment to attend to Grub for the second.
    Reply
  • SomeoneElse23
    I have a solution. Don't use Windows 11!

    Happy with Win10 and 0patch here.
    Reply
  • USAFRet
    SomeoneElse23 said:
    I have a solution. Don't use Windows 11!
    With every OS, every version, every maker (Apple/MS/Linux), there are some outlying systems that have an issue during updates.

    Every single one, since PCs were a thing.
    Reply
  • TechieTwo
    No one abuses their OS customers better than Microsoft. They go to entra lengths to deliver for you. ;)
    Reply
  • JamesJones44
    USAFRet said:
    With every OS, every version, every maker (Apple/MS/Linux), there are some outlying systems that have an issue during updates.

    Every single one, since PCs were a thing.
    While bugs are common for all OSs, bricking devices isn't common, but with Windows 11, it has become somewhat common.
    Reply
  • USAFRet
    JamesJones44 said:
    While bugs are common for all OSs, bricking devices isn't common, but with Windows 11, it has become somewhat common.
    No...reporting of it maybe more common.
    Reply
  • Notton
    USAFRet said:
    With every OS, every version, every maker (Apple/MS/Linux), there are some outlying systems that have an issue during updates.

    Every single one, since PCs were a thing.
    One difference though.
    Linux distros don't force updates on you and it's always optional.
    Whereas 24H2 was a forced update.
    Reply