Microsoft issues fix as Windows 11 25H2, 24H2 KB5066835, KB5065789 break many IIS websites

Earlier today, Microsoft confirmed that a Windows 11 24H2 upgrade block has finally been removed as issues with a third-party driver have been resolved. However, the company has also posted some bad news alongside it.

The company has confirmed that Windows 11 24H2 as well as version 25H2, break many IIS (Internet Information Services) websites after the recent October 2025 Patch Tuesday update and its preview update. As a result, localhost loopbacks and various other IIS-based authentications are broken at the moment due to conflicts between the Windows updates and the HTTP stack (or http.sys) driver. Consequently, an "ERR_CONNECTION_RESET" error message is displayed.

Microsoft has explained: "Following installation of updates releases on or after September 29 (KB5066835 / KB5065789), server-side applications that rely on HTTP.sys may experience issues with incoming connections. As a result, IIS websites might fail to load, displaying a message such as "Connection reset - error (ERR_CONNECTION_RESET)", or similar error. This includes websites hosted on http://localhost/, and other IIS connections."

The company has added that the problem may occur due to a "variety of conditions" like "device's internet connectivity, as well as timing of recent update installation and device restarts" and as such it may not appear in every environment.

Microsoft says that it is working on a fix but for now it has asked to deploy a known issue rollback as a workaround. It writes:

IT admins can resolve this issue ... by installing and configuring the Group policy listed below. The special Group Policy can be found in Computer Configuration > Administrative Templates > [Group Policy name].

 

Group Policy downloads with Group Policy name:

 

• Download for Windows 11, version 24H2, Windows 11 25H2 and Windows Server, version 2025 - Windows 11 24H2, Windows 11 25H2 and Windows Server 2025 KB5066835 251015_22001 Known Issue Rollback.msi

You can view the issue here on the Windows Health dashboard web page on Microsoft's official site.

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Posted Saturday 18 October 2025 at 3:44 am AEST (my time).

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