Win11 24H2 (Ent/IOT LTSC) - Error 0x800f0991 on recent Cumulative Updates (KB5094126)

[bseklecki_ge]

Anyone else receiving error 0x800f0991 when integrating May/June Win11 Cumulative Update?

The bizarre thing is that it give an error, marks it as partial failure (The SSU component of the CU seems to be installed) - ambiguous results if one is in a hurry/distracted.

This is v2026.3.10844 ; I'm updating to v2026.07.11258 now to try again and report back.

Our failure is with [KB5094126] ; the latest approved CU (OT being behind the curve a bit)

 

[scaramonga]

0x800f0991 appears when the system fails to install cumulative updates, relating to corrupted system files, broken update components, or missing dependencies.

Start with the base Enterprise LTSC 2024 image, build - 26100.1742 (this is the only image up to date for IOT) from MS. Do not use any other variant!, or one modified by yourself

Make sure correct 'setup' key is entered in for IOT - KBN8V-HFGQ4-MGXVD-347P6-PDQGT (setup key, not activation) in NTLite.

I run this system, and it integrates (to 8737) just fine

I include my preset, which works for me, and have no issues.

Below is all updates to bring OS up to date, minus the rot that is Defender.

I'd hold off though, as 'Patch Tuesday' is today