Posted on 09/20/2025 10:27:12 AM PDT by ducttape45
Microsoft has confirmed that the September 2025 Windows security updates are causing connection issues to Server Message Block (SMB) v1 shares.
The list of platforms affected by this known issue is quite extensive, as it includes both client (Windows 11 24H2/23H2/22H2 and Windows 10 22H2/21H2) and server (Windows Server 2025 and Windows Server 2022) platforms.
In a service alert seen by BleepingComputer, Microsoft said this known issue affects those connecting to SMBv1 shares over the NetBIOS over TCP/IP (NetBT) networking protocol.
"After installing the September 2025 Windows security update (the Originating KBs listed above) or later updates, you might fail to connect to shared files and folders using the Server Message Block (SMB) v1 protocol on NetBIOS over TCP/IP (NetBT)," the company said.
"This issue can occur if either the SMB client or the SMB server has the September 2025 security update installed."
Microsoft is now working to resolve this issue, and until a fix is available, it has provided impacted customers with a temporary workaround.
This requires them to allow traffic on TCP port 445, which will cause the Windows SMB connection to resume successfully by switching to using TCP instead of NetBT.
The SMBv1 networking protocol was superseded by SMBv2 and later protocols in 2007 and deprecated in 2014. SMBv1 is no longer installed by default since the release of Windows 10 version 1709 and Windows Server version 1709.
Microsoft began disabling the 30-year-old SMBv1 file-sharing protocol by default for Windows 11 Home Insiders in April 2022. The first plans to remove SMBv1 from most Windows versions were announced in June 2017, after initially disabling it in internal builds of Windows Server 2016 and Windows 10 Enterprise.
Microsoft has been warning admins to remove support for SMBv1 on their network for years, as it lacks the security improvements added to newer versions of the protocol, including pre-authentication integrity checks to prevent man-in-the-middle (MiTM) attacks, insecure guest authentication blocking, protection against security downgrade attacks, and more.
These warnings followed the 2017 leak of multiple NSA exploits designed to exploit weaknesses in the SMBv1 protocol, which allowed commands to be executed on vulnerable servers with admin privileges.
Some of these exploits, such as EternalBlue and EternalRomance, were later deployed in the wild by WannaCry, NotPetya, TrickBot, Emotet, Olympic Destroyer, and Retefe malware in destructive attacks or for credential theft.
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To say I'm angry is an understatement, I'm livid. This wouldn't be a problem for me if I wasn't concerned in getting the ESUs until next year, because to do so my PC had to be fully updated, and as a result I hit with this problem. The only way I can now share files between my PCs is to load them on an external storage device.
I've tried all of the fixes mentioned in this article and many others, but nothing works. Even networked printers have been taken offline because of it.
Please share your experiences and fixes if you have any. Thanks for your time.
Glad I’ve upgraded to Windows 7.
And the hits just keep coming...
Need more from India ,LOL
SMBv1 has been deprecated for decades. We’re up to SMBv3.1.1. The security issues with SMBv1 are terrible. This has been a long time coming. If you’re having issues with SMBv1, you’re using very old hardware. EXCEPTIONALLY old.
I can tell you that SMBv1 is so lacking in security that threat actors actively seek it out. It’s trivially easy to compromise. I’d advise migrating your data to more modern storage lest you become the next victim.
Yeah, we sure need those “highly” skilled Indian programmers. /spit
Nobody should be using SMBv1.
Trust me, I’m about ready to go back to W7.
I took all down, used the HD as a data disk, installed Windows 10 on a new HD with no updates allowed, recovered all her data and all is well for the cost of a little time and a new HD. And no new software et alia.
Microsoft as an OS isn't so bad, per se. Microsoft as a company sucks, thinking they can constantly tinker and never screw up.
Server Message Block version 1 and the others as well can simply be disabled. You won;t find that info in the headlines, though. The article didn't, but some informed comments at the bottom did.
I always pause the automatic updates on my Win 10 machine. That postpones them for a few weeks.
With any luck they’ll have the bugs fixed by then.
I looked into try to roll back the software, but the offending update was not present to do so. It’s somehow “baked” into the O/S and can’t be removed. Blast them. I’m pausing all updates until they fix this mess cuz this is bigger then SMB1.
“I’m about ready to go back to W7.”
I have a Win. 7 desktop and laptop.
Bought refurbished Win 10 desktop and laptop just to see how I like it. 10 sucks, and that Edge thing is a demon that possesses it.
I revert back to the 7 devices.
I have a laptop also but it doesn't have W7, just 10 and Linux. I can't actually program W7 onto it but I think if I put a SSD with W7 already on it, in it, I can get it to work. I'm gonna try that and see what happens one of these days.
Windows sucks. Why isn’t there a reasonable plug-an-play alternative? Tell me now that capitalism works! All we did with Windows is made the monster Gates filthy rich.
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