Microsoft has linked latest stories of Home windows 11 boot failures after putting in the January 2026 updates to beforehand failed makes an attempt to put in the December 2025 safety replace, which left techniques in an “improper state.”
The boot failures had been first reported earlier this month after customers put in the January 2026 Patch Tuesday cumulative replace, KB5074109, on Home windows 11 variations 25H2 and 24H2.
After putting in the replace, impacted techniques failed to start out and displayed a BSOD crash display with a cease error of “UNMOUNTABLE_BOOT_VOLUME” code.
In a brand new replace first noticed by Susan Bradley of AskWoody, Microsoft says its investigation discovered that gadgets affected by latest boot errors had been beforehand unable to put in the December 2025 safety replace.
When the failed replace was rolled again, Home windows was left in an unstable state, or “improper state.”
“Current investigations have decided this concern can happen on gadgets that failed to put in the December 2025 safety replace and had been left in an improper state after rolling again the replace,” reads the up to date advisory.
“Making an attempt to put in Home windows updates whereas on this improper state may end result within the gadget being unable as well. We’re engaged on a partial decision that can stop further gadgets from leading to a no-boot state of affairs in the event that they attempt to set up an replace whereas on this improper state.”
“Nonetheless, this partial decision won’t stop gadgets from stepping into the improper state within the first place, nor will it restore gadgets which are already unable as well.”
The corporate says it continues to research why some gadgets fail to put in Home windows updates or find yourself on this improper state following a rollback.
Microsoft says that the problem is presently restricted to bodily gadgets, with no stories of digital machines being impacted.
BleepingComputer contacted Microsoft with additional questions on this concern and can replace the story if we obtain a reply.
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