Windows 11 update breaks localhost, prompting mass uninstall workaround
- Reference: 1760620297
- News link: https://www.theregister.co.uk/2025/10/16/windows_11_update_localhost/
- Source link:
The problem first surfaced on Microsoft's own [1]support forums and quickly spread to [2]Stack Overflow and [3]Server Fault after the October 2025 cumulative update (KB5066835) landed, which appears to have severed Windows' ability to talk to itself.
Developers describe HTTP/2 protocol errors and failed connections affecting everything from [4]ASP.NET builds to [5]Visual Studio debugging sessions.
[6]
The bug, introduced in build 26100.6899, has been traced to HTTP.sys, the Windows kernel component that handles local HTTP traffic. Developers have found that uninstalling KB5066835, and in some cases its sibling KB5065789, restores localhost functionality.
[7]
[8]
Others have discovered a temporary workaround that involves manually disabling HTTP/2 in the registry, which works but feels a bit like using a sledgehammer to swat a fly.
At the time of writing, Microsoft had yet to acknowledge the issue. Users report mixed results when trying to reinstall the patch or roll forward to newer builds. The problem appears to vanish on clean installs of Windows 11 24H2, suggesting that the error stems from a conflict in how the update interacts with existing system configurations, rather than being a universal bug.
[9]
In the meantime, moderators on Stack Overflow have already locked multiple posts and Server Fault threads are filled with frustrated devs trying to get their local servers running again.
[10]Schleswig-Holstein waves auf Wiedersehen to Microsoft stack
[11]What do we want? Windows 10 support! When do we want it? Until 2030!
[12]Who gets a Mac at work? Here's how companies decide
[13]No account? No Windows 11, Microsoft says as another loophole snaps shut
All this comes as Microsoft pushed its final update for Windows 10 this week, officially ending support for the decade-old OS and [14]urging users to move to Windows 11.
The transition hasn't exactly been buttery smooth. Microsoft's Windows 11 media creation tool also [15]stopped working the day before, potentially affecting users trying to upgrade, and the same patch cycle saw [16]end-of-support deadlines for Office 2019 and multiple server products.
All this means that, within the same week, Microsoft's installer broke, its new OS borked local development, and Redmond's multimillion-dollar upgrade push instead highlighted how fragile its ecosystem still is.
It's almost enough to make you nostalgic for Clippy. We said almost . ®
Get our [17]Tech Resources
[1] https://learn.microsoft.com/en-us/answers/questions/5585563/localhost-not-working-anymore-after-2025-10-cumula
[2] https://stackoverflow.com/questions/79790827/localhost-applications-failing-after-installing-2025-10-cumulative-update-for-w
[3] https://serverfault.com/questions/1193405/http-2-protocol-error-connecting-to-localhost-web-sites
[4] http://asp.net
[5] https://www.theregister.com/2025/10/15/vc_code_extension_leaks/
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aPEWlYU0R8e6rdRD7ZpgugAAARA&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aPEWlYU0R8e6rdRD7ZpgugAAARA&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[8] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aPEWlYU0R8e6rdRD7ZpgugAAARA&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/oses&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aPEWlYU0R8e6rdRD7ZpgugAAARA&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[10] https://www.theregister.com/2025/10/15/schleswig_holstein_open_source/
[11] https://www.theregister.com/2025/10/14/protest_outside_microsoft_brussels/
[12] https://www.theregister.com/2025/10/11/who_gets_mac_at_work/
[13] https://www.theregister.com/2025/10/07/windows_11_local_account_loophole/
[14] https://www.theregister.com/2025/10/09/business_windows_10_eol/
[15] https://www.theregister.com/2025/10/13/windows_11_media_creation
[16] https://www.theregister.com/2025/10/16/windows_10_office_and_servers/
[17] https://whitepapers.theregister.com/
Re: "Microsoft's quality control department"
"They were fired a decade ago."
More precisely, testing was outsourced to users.
It sounds as if the testers are reporting the bugs they found exactly as intended.
Maybe intentional
It just may be that the access to localhost has been deprecated in favour of using the Microsoft Cloud and Clippy AI infrastructure. That would at least make sense, from a strategic point of view.
And people actually pay
... for this crap?
You certainly couldn't give it away. ;-)
Of course we all know the permanent fix
Linux (Mint for desktop, Debian for server) is thataway --->
Because even when (or if) MS fix this, we know it won't be long before the next one.
Jupyter-notebooks
Wonder if it will break the above, they seem to use localhost?
Re: Jupyter-notebooks
Localhost is used by a huge amount of stuff, though this does seem to be limited to HTTP/2 and not all localhost.
But yes, almost certainly.
When you enter the integration and test phase of any product it's not unusual to find bugs; that's what testing's for, isn't it?
Does/did Microsoft ever get past that point ?
"update [...] appears to have severed Windows' ability to talk to itself"
Odd: I'd believed most jurisdictions now prohibit lobotomy.
Not if it's self inflicted ;)
Honesty WTF is with Microsoft Windows 11? Even Windows 10 didn't have this many updates acting like malware.
They are re-writing several core parts of the kernel from scratch since there is little to no documentation, and in some cases they don't even have the source code, only compiled binaries.
Ah! That explains why it's getting progressively slower every time updates are applied.
Beyond satire, beyond parody
M$ are a fucking circus.
How does it feel to still be a "customer"? Are you proud? Are you still threatening to go Mac or Linux, or are you just going to keep on making excuses for your "habit"?
Functionality now known as
localghost
Re: Functionality now known as
As opposed to the 'localheist' that is Telemetry?
"Microsoft's quality control department"
They haven't been caught napping.
They were fired a decade ago.
This is the result.