How Do I Fix the SMBv1 File Sharing Error from Recent Windows 11 23H2 KB5065790 Update?

Why Can’t I Access My Network Drive After the Windows September KB5065790 Update?

Have you found yourself unable to access files on your network after a recent Windows update? A fix has been released for some systems, and this guide will explain what happened and what you can do about it.

What Problem Did the Update Cause?

On September 9, 2025, Microsoft released routine security updates for Windows 10 and Windows 11. These updates are important because they fix bugs and protect your computer from security threats. However, this particular update also caused an unexpected problem for some people. They suddenly could not connect to network folders or shared files.

This issue happened because of a change made to a file-sharing protocol called Server Message Block, or SMB. Specifically, the update affected the oldest version, SMBv1. The update was intended to fix a security vulnerability, but it unintentionally broke connections for systems still using this outdated protocol. Shortly after the update was released, people began reporting that their network shares were no longer accessible. The problem was linked to a fix for a security risk known as CVE-2025-55234, which deals with how Windows SMB handles connections.

Microsoft’s Confirmation of the Issue

Microsoft quickly acknowledged the problem. In an official service alert with the ID WI1152308, the company confirmed that users might fail to connect to shared files using the SMBv1 protocol after installing the September 2025 security update. This alert specified that the issue occurred when the connection used an older method called NetBIOS over TCP/IP (NetBT).

This problem did not affect everyone. It was specific to certain setups and Windows versions. The issue was confirmed for the following systems:

• Windows 11, versions 22H2 to 24H2
• Windows 10, versions 21H2 to 22H2
• Windows Server 2022
• Windows Server 2025

If your computer uses a newer version of the SMB protocol, like SMBv2 or SMBv3, you were not affected by this bug. The problem was limited only to connections that relied on the old SMBv1.

Understanding SMBv1 and Why It Is a Problem

To understand the issue, it helps to know what SMB is. Server Message Block is a network protocol, which is like a set of rules that computers use to communicate. It allows applications on a computer to read and write to files and to request services from server programs in a computer network. When you access a shared folder on another computer or a network drive, you are likely using SMB.

SMBv1 is the original version of this protocol, first created in the 1980s. Because it is so old, it has significant security weaknesses that modern protocols have fixed. For this reason, Microsoft has been encouraging users to move away from it for years. In fact, newer versions of Windows do not even install SMBv1 by default.

However, many older network devices still use it.

• Old Network Attached Storage (NAS) devices
• Older models of printers or scanners with network capabilities
• Legacy business applications

If your network includes any of these older devices, you might have been forced to keep SMBv1 enabled, which is why the September update caused problems for you. This bug serves as a strong reminder that relying on outdated technology can lead to unexpected issues.

The Fix Is Here for Some Windows 11 Users

On September 23, 2025, Microsoft released a preview update that fixes this SMBv1 bug. This update is identified by the code KB5065790. It is currently available only for users running Windows 11 version 23H2.

In the update notes, Microsoft states that it “addresses an issue where you might not be able to connect to shared files and folders if you’re using the Server Message Block (SMB) v1 protocol.” If you are using Windows 11 23H2, you can install this optional preview update to resolve the network connection problem immediately.

A “preview” update is an optional update released in the latter half of the month. It contains fixes and improvements that will be included in the next month’s mandatory security update. Installing it is a good way to get an early fix for a problem that is affecting you.

What if I Use a Different Version of Windows?

If you are using Windows 10 or a different version of Windows 11, the fix is not yet available for you in a dedicated update. Microsoft is working on it, and it is expected to be released for all other affected Windows versions with the next scheduled security update. This is planned for October 14, 2025.

Until then, you have two main options. You can either wait for the official fix in October or use a temporary workaround that Microsoft suggested. The workaround involves a small change to your network settings. It forces the SMB connection to use TCP directly instead of the older NetBT method. To apply this, your network firewall must allow traffic on TCP port 445. For most home networks, this is already the case. This workaround should restore your access to the network shares.

A Good Time to Move Away from SMBv1

This entire situation highlights the importance of moving away from SMBv1. Because it is old, it does not support the security features of modern SMB versions, such as encryption. This makes your network more vulnerable to attacks.

You should check if any of your devices require SMBv1 and plan to upgrade them. A newer NAS device or printer will use the much safer SMBv2 or SMBv3 protocol and will not be affected by issues like this one. Disabling SMBv1 on your Windows computers is a recommended security step.

You can check if SMBv1 is installed on your system and disable it.

1. Click the Start button and type “Windows Features.”
2. Select “Turn Windows features on or off.”
3. In the new window, scroll down to find “SMB 1.0/CIFS File Sharing Support.”
4. If the box is checked, SMBv1 is active. Uncheck the box to disable it.
5. Click OK and restart your computer for the change to take effect.

By disabling SMBv1, you make your computer more secure. If you find that you lose access to a network device after disabling it, that means the device requires the old protocol. In that case, you should prioritize replacing that device to improve your network’s security.