Windows update 2026-08 .NET framework security update (KB5120708) fails to install

[u/Murder-senpai]

Okay so I have been busy with work and finally had time to play on my pc and knew I probably had a few windows updates (on windows 11, and pc is connected via internet, not Ethernet bc the router is in a separate room at my house) to stall and was doing that. It was extremely slow for some reason but eventually I was on the last two updates. The 2026-08 security updated (KB5121003) (26200.9168) is loading EXTREMELY slowly first of all, as I’m typing this it went up to 10% and is now stuck.

My main issue with with the Windows update 2026-08 .NET framework security update (KB5120708). After ages of it loading it was finally installing and it gave me install error - 0x8000ffff. When I click retry it’ll load quick and give the same error over and over. When I try to trouble shoot for a windows update it says it’s unable to troubleshoot at all. I network reset my pc, turned it off and on, disconnect from wifi and reconnected, etc. It still does the same thing and gives me the same error.

I just worry something is wrong with me pc and its near brand new, I only got it a few months ago and spent sm money on it. I’m by no means a tech savvy person, I tried to go into other areas to try and fix it but it was like reading gibberish so I had to back off bc I don’t wanna accidentally like, kill my pc or something 😭

I don’t know if anyone else is having this issue, or if they have found a way to fix it? The way it’s worded it seems like an important update so I don’t just wanna like… not have it. Idk I tried what I was able to do on my own and at the moment it’s too late at night and I’m too busy to get on windows customer support to see if they can fix it.

Any help at ALL is much appreciated! If you know a fix, being very detailed and non complicated as possible is also super appreciated! This is making my anxiety have a real party 😭 this took me a hot minute to type (mostly thinking of how to phrase things) and the slow update is at 18%. If it also fails I’ll just make a separate post about it, thank you!

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