After installing the September 2025 KB5065426 update, file and printer sharing suddenly stops working for many. Shared folders ask for a password that never works. Printers vanish from the network. Devices that always connected smoothly now fail. There are countless such reports across forums.
The good news is you can troubleshoot it. This guide walks through the causes, what Microsoft has admitted, and the steps you can take to fix it!
Why does File and Printer Sharing break in KB5065426?
Microsoft has officially acknowledged that the update affects certain types of file sharing. The main trigger is the way Windows handles older versions of SMB (Server Message Block), the protocol behind file and printer sharing. If your setup relies on SMBv1 over NetBIOS, the update may block it.
That is not the only reason, though. Many users also report that the update resets sharing settings, changes the network profile from Private to Public, or creates problems when machines share the same Security Identifier (SID).
So while Microsoft describes the issue as an SMB transport problem, the real-world impact is broader!
Microsoft’s suggested workaround
Microsoft has suggested a temporary workaround. The idea is to let SMB traffic bypass NetBIOS and go directly through a newer transport. To do that, you need to allow traffic on TCP port 445.
Here’s how:
For Inbound Rule
- Press the Windows key > type wf.msc > press Enter > click Inbound Rules in the left panel > click New Rule > select Port > click Next > select TCP > choose Specific local ports > type 445 > click Next > select Allow the connection > click Next > tick Domain and Private (leave Public unchecked) > click Next > type a name like Allow SMB TCP 445 Inbound > click Finish.
For Outbound Rule
- Click Outbound Rules in the left panel > click New Rule > select Port > click Next > select TCP > choose Specific remote ports > type 445 > click Next > select Allow the connection > click Next > tick Domain and Private (leave Public unchecked) > click Next > type a name like Allow SMB TCP 445 Outbound > click Finish.
This forces SMB to use a more modern channel, which may restore sharing.
Also Read: How to Fix the 0x80073712 Windows Update Error
Other Fixes You Can Try
Depending on your setup, you may need to try more than one fix. Let’s walk through the most common ones.
1. Check network profile and sharing settings
Sometimes the update switches your network to Public and disables sharing. To fix it:
- Open Settings and go to Network and Internet.
- Select your active network and change the profile to Private.
- Go to the Advanced sharing settings under Advanced network settings.
- Turn on Network discovery and File and printer sharing.
- Restart the PC and try again.
2. Fix duplicate Machine SIDs
If your machines were cloned or imaged without resetting their SID, they might not authenticate after the update. To solve this:
- On one of the affected machines, run Sysprep or a SID-changing tool.
- Reboot the system so it generates a new unique SID.
- Repeat this for any other duplicates.
- Test file sharing between the machines again.
3. Re-enable legacy options
Some devices, like old printers or NAS units, only support SMB1 or guest access. If nothing else works:
- Press the Windows key, type Windows Features, and select the Turn Windows features on or off option.
- Scroll down and check SMB 1.0/CIFS File Sharing Support, and then click OK.
- Wait for Windows to apply the changes.
- Click Restart now when prompted.
Be careful with this option. It makes your network less secure. Treat it as a temporary solution while you plan to replace old hardware.
4. Uninstall KB5065426
If sharing is critical and none of the above helps, removing the update may be your fastest path forward.
- Open Settings > go to Windows Update > click on View update history > select Uninstall updates > find KB5065426 > click Uninstall next to it > confirm the change > restart your PC.
This usually restores sharing, but you will also lose the security patches that came with the update.
What Microsoft has not fixed yet?
At this stage, Microsoft has only offered the port 445 workaround. They say a full resolution will come in a future update, but it is not available yet. That means users are left juggling settings, workarounds, and, in some cases, rolling back updates just to keep basic sharing working.
No. The main issue Microsoft confirmed involves SMBv1 over NetBIOS. SMB2 and SMB3 should keep working, but some users still report credential errors and blocked access even with newer versions.
Port 445 should only be allowed on trusted private networks. Leaving it open on public networks or the internet is a major security risk because attackers often target it. Restrict access to your local subnet only.
Removing the update usually restores sharing, but you lose the security fixes it contains. If you uninstall it, pause updates to avoid it being reinstalled until Microsoft ships a permanent fix.
KB5065426 was designed to make Windows more secure, but it has left many people without working file and printer sharing. Microsoft’s official workaround is a start, but it does not cover every case. Until a proper fix is released, you will need to rely on the steps above.
Here is the practical order: check your network settings first, then address duplicate SIDs, try the port 445 workaround, and only fall back on enabling legacy features or uninstalling the update if you absolutely have to!
Keep an eye on future Windows updates. A permanent fix is expected, but for now, these steps can keep your network running.
With over five years of experience in the tech industry, Kazim excels at simplifying complex topics, making them accessible to tech enthusiasts and general readers alike. He has contributed to several renowned publications worldwide, including WindowsReport and Allthings.how, bringing insightful coverage of key developments in the field.
Kazim has extensively covered the Windows ecosystem, from the early days of Windows 7 to Windows 11. Unlike many in the field, he’s optimistic about Windows 11, calling it the most user-oriented iteration to date.
When he’s not writing, you’ll find Kazim planning weekend getaways or diving into tech verticals beyond his expertise.
