Microsoft says the Windows 11 boot failure bug is linked to another buggy update: 'This issue can occur on devices that failed to install the December 2025 security update and were left in an improper state'
Well, don't I have egg on my face. After writing an article yesterday wherein I pointed out that Windows 11 is "currently in a reasonable state", it appears the OS now has something of a stacked bug problem.
We previously reported on a bug that Microsoft said was creating a "limited number of reports" over a boot failure issue, in which users were greeted with an "UNMOUNTABLE_BOOT_VOLUME" stop code after installing the January 2026 Windows security update (KB5074109).
However, according to Bleeping Computer, Microsoft now says that the update-based failure seems to be linked to a previous security update bug. Per a Microsoft business account-locked advisory spotted by an AskWoody forum member:
"Recent investigations have determined this issue can occur on devices that failed to install the December 2025 security update and were left in an improper state after rolling back the update.
"Attempting to install Windows updates while in this improper state could result in the device being unable to boot. We are working on a partial resolution that will prevent additional devices from resulting in a no-boot scenario if they try to install an update while in this improper state.
"However, this partial resolution will not prevent devices from getting into the improper state in the first place, nor will it repair devices that are already unable to boot", says MS.
So, it looks like it's a failed update that causes the next update to, err, fail. This sounds like a particularly frustrating problem, although if you keep your machine updated on the regular there's a good chance you're already on the new update without this issue.
Or you can't read this piece on your desktop PC because it won't boot. Ugh. While Windows 11 is arguably pretty stable these days (Microsoft certainly thinks so), it's bugs like these that make users wary, and rightly so. Hopefully Microsoft's "partial resolution" eventually becomes a full one, although by the looks of its efforts so far, it seems like a full re-install may eventually be in order. It's not a great look, I grant you.