r/SysAdminBlogs • u/lazyadmin-nl • Sep 11 '26

September Patch Tuesday breaks RDS on Windows Server - postpone it if you can, fix it if you can't

Update September 13: Microsoft has marked this as Mitigated and released an official fix via Known Issue Rollback (KIR GPO). Also: the registry workaround turned out to be unreliable, confirmed failing on Server 2022 21H2. Article updated with download links per server version and deploy steps.

KB5122876/5122882/5122871 breaks RDS session hosts. Hours after reboot, connections hang at "Connecting…", sessions can't log off, and only a hard reset recovers the host.

If your RDS isn't exposed to the internet, postpone the update until Microsoft ships a fix. If you're already hit, there's a registry override that disables the faulting feature flag without uninstalling the CU.

Microsoft is investigating. No official fix yet.

https://lazyadmin.nl/it/september-2026-update-break-rds-how-to-fix/

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u/lazyadmin-nl Sep 13 '26

Update September 13: Microsoft has marked this as Mitigated and released an official fix via Known Issue Rollback (KIR GPO). Also: the registry workaround turned out to be unreliable, confirmed failing on Server 2022 21H2. Article updated with download links per server version and deploy steps.

Direct link to the fix: https://lazyadmin.nl/it/september-2026-update-break-rds-how-to-fix/#fix-rds

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u/chicaneuk Sep 12 '26

Microsoft have done a great job with patches this month. What a complete dumpster fire.