Windows 10/11 – Unable to access a shared folder

Need to access shared folders on a NAS? Except that from your Windows 10 or Windows 11 system you have this error message

You cannot access this shared folder because your company’s security policies block unauthenticated guest access »

Here is a complete tutorial to unblock the situation.

Problem connecting to shared folders

In my case the shared folders are stored on a QNAP-NAS the files are not freely accessible, you must authenticate with an account + password (accounts created on the NAS).

However I noticed that there were connection problems for the files accessible without authentication.

Strangely the problem is not present on different computers, the computers in Windows 11 or with a recent version of Windows 10 are impacted.

To be more specific about the diagnosis, here is what happens.

When I go looking samba sharing in UNC path (for example \nas) I can see the root folders. But as soon as I try to open a file I am confronted with the following Windows error message:

You cannot access this shared folder because your company’s security policies block unauthenticated guest access

Pings and access to NAS via web interface work perfectly.

No Access to Shared Folders on Windows 10 & Windows 11 – The Solution

To solve this problem, you must modify the local group policy (GPO for workstations integrated into a Active Directory domain)

On your computer, press Windows key + R and enter

gpedit.msc

We will navigate through the following parameters: Computers > Administrative Template > Network > Lanman Workstation

local group policy
You can change the policy on each workstation.

Then we will modify the parameter Enable insecure guest logins you have to select “Activate”

Reconnect, it should work.

For those with a large fleet you can directly modify the setting using GPO on your domain controller.