Windows 11 24H2 breaks connection to some third-party NAS with SMB

A broken Windows 11 logo indicating bugs

Microsoft recently released Windows 11 version 24H2 in the Release Preview Channel, which means more users can try the upcoming feature update before its public rollout. If you are one such user, you may experience problems with connecting to a third-party NAS. To address confusion and clarify things, Microsoft published a blog post with all the details.

In a nutshell, Windows 11 version 24H2 contains two important security changes: SMB signing is now required on all connections to prevent network tampering, and guest fallback is now disabled on Windows 11 Pro to improve security when connecting to untrustworthy devices. Microsoft says those two changes will make "billions of devices more secure," but at the cost of some headaches for existing users.

According to the post from Microsoft, users may experience the following issues on systems with Windows 11 24H2 when connecting to third-party network-attached storage:

If signing is not supported	If guest access is required
0xc000a000 -1073700864 STATUS_INVALID_SIGNATURE The cryptographic signature is invalid	You can't access this shared folder because your organization's security policies block unauthenticated guest access. These policies help protect your PC from unsafe or malicious devices on the network 0x80070035 0x800704f8 The network path was not found System error 3227320323 has occurred

Security changes that may mess up your NAS are not new—they have been in testing in Canary and Dev for over a year now. However, with Windows 11 24H2 getting closer and more users testing it, Microsoft decided to provide users with detailed instructions on how to fix things. Also, the company says its goal is to protect your data, "not to help third parties sell you unsafe products."

Affected customers can mitigate the errors by enabling SMB signing in their NAS, disabling guest access, setting a username and password in their NAS control panel, updating the firmware (if the necessary options are missing), or buying a newer, safer model.

Of course, there are other solutions that are less safe. They involve turning off the SMB client signing requirement and the guest fallback protection. Microsoft understands that not everyone can address the problem in a safe way, so there are also temporary workarounds, which you can find here.

Another thing in Windows 11 24H2 that might surprise you is the AC-3 codec or the lack of it. Microsoft quietly announced that its upcoming update will remove the AC-3 codec for surround sound.