When will the new ' 2025-08 Cumulative Update for Windows 10 Version 21H2 for x64-based Systems (KB5066188)' be available on WSUS? i see it on the download.

Hi Kian wei Ma,

I hope this message finds you well.

You're correct—KB5066188, the August 2025 Cumulative Update for Windows 10 Version 21H2 (x64), is listed on the Microsoft Update Catalog website. However, it's not uncommon for updates to appear there before they are fully propagated to Windows Server Update Services (WSUS).

Typically, cumulative updates are synchronized to WSUS within 24 to 72 hours after public release, depending on regional replication and server sync schedules. If you're not seeing it yet, we recommend manually triggering a WSUS sync and verifying that your classifications and products are correctly configured to include Windows 10 updates.

You can also check the WSUS synchronization logs to confirm whether the update was skipped or delayed. If it still doesn’t appear after a few days, it may be worth reviewing the Microsoft Update Services health dashboard for any known delays.

Let us know if you'd like assistance reviewing your WSUS configuration or manually importing the update.

Best regards,

Quinnie Quoc.

It's an out of band update not available over WSUS - https://www.ajtek.ca/blog/why-kb-xxxxxxx-isnt-showing-up-in-wsus/

Use Import-WsusUpdate to import it to the WSUS server

https://www.ajtek.ca/free-tools/import-wsusupdate/

Import-WsusUpdate -KB KB5066188 -x64 -Filter "Windows 10 22H2"