Issue where network credentials are required when accessing a shared folder after the Windows update in May 2025

Question

This is an elementary school computer lab environment. One teacher PC and 30 student PCs are connected to the same switching hub and are on the same local area network (LAN).

A specific folder on the teacher’s PC is shared so that multiple student PCs can access it and upload student files. Until around May 2025, before a Windows update was installed, there were no issues accessing the shared folder.

However, since the update, when student PCs attempt to access the shared folder on the teacher’s PC, a “Enter network credentials” prompt keeps appearing and access is blocked. As a result, students are unable to download class materials, causing classes to come to a complete halt and creating a very serious disruption.

I have heard that reverting to a previous version may resolve the issue, but since a significant amount of time has passed after the update, it is no longer possible to roll back to a previous build or uninstall the update. At the same time, we cannot simply stop updates for security reasons, leaving us in a very difficult situation with no clear solution.

[Actions Taken So Far]

1. Disabled “Password-protected sharing” in the Advanced sharing settings on the teacher’s PC.
2. Tested by changing the network profiles on both the teacher and student PCs to “Private network” and “Public network.”
3. Even after creating a separate user account (with a password) on the teacher’s PC and adding it to the shared folder’s permissions and Security tab, student PCs still either prompt for credentials or deny access. The same issue occurs even when the “Guest” account is enabled and granted permissions.

Despite taking the basic measures described above, the system still continues to request network credentials.

[Inquiry] We suspect that recent updates have changed the security policies related to network sharing (SMB). We would greatly appreciate guidance on a precise solution or additional configuration (such as Local Group Policy settings) that would allow seamless access to the shared folder as before, without requiring manual entry of credentials. We sincerely look forward to your response.

Answer 1

The behavior is consistent with tightened SMB and authentication policies introduced by recent Windows updates. Anonymous/guest access to shares is being blocked, so clients are forced to authenticate.

To restore seamless access in a small, non-domain lab where security policy allows it, configure the teacher PC and (if needed) student PCs as follows.

1. Allow guest/unauthenticated access to SMB shares

On each Windows 11 PC that must access the share without credentials:

Method 1: Registry (if Local Group Policy Editor is not available)

1. Open Registry Editor on the student PC.
2. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\LanmanWorkstation
   • If LanmanWorkstation does not exist, create it under Windows.
3. In LanmanWorkstation, create a new DWORD (32-bit) Value named: AllowInsecureGuestAuth
4. Set Value data to 1.
5. Close Registry Editor and restart the PC.

This explicitly enables insecure guest logons for SMB from that client.

Method 2: Local Group Policy (if available on the client)

1. Run gpedit.msc.
2. Go to: Computer Configuration → Administrative Templates → Network → Lanman Workstation.
3. Open Enable insecure guest logons.
4. Set it to Enabled and apply.
5. Restart the PC.

This has the same effect as the registry setting above and allows connecting to guest/anonymous shares without credentials.

2. Ensure NetBIOS/SMB name resolution works (if using computer name)

If access by IP works but by computer name does not, enable NetBIOS over TCP/IP on the student PCs:

1. Open Network and Sharing Center → Change adapter settings.
2. Right-click the active adapter → Properties.
3. Select Internet Protocol Version 4 (TCP/IPv4) → Properties.
4. Select Advanced → WINS tab.
5. Select Enable NetBIOS over TCP/IP → OK → OK.

This helps clients locate the teacher PC by name when browsing to \\TeacherPCName\Share.

3. Prefer SMB2/SMB3 and NTLMv2 (if NAS or older SMB is involved)

If any device in the path still uses SMBv1 or older authentication, configure it (where possible) to use SMB2 or SMB3 and NTLMv2 only. This aligns with current Windows security expectations and avoids SMBv1-related connectivity issues mentioned in recent updates.

4. If using a passworded account instead of guest

If guest access is not acceptable and a dedicated account on the teacher PC should be used:

• Confirm that the account is enabled, has a non-expired password, and is granted both Share and NTFS (Security tab) permissions to the shared folder.
• From a student PC, when prompted for credentials, enter:
  • Username: TEACHERPCNAME\AccountName
  • Password: the password set on the teacher PC.

If the account is disabled or the password expired, Windows will repeatedly prompt or deny access, similar to the behavior described in the Visual Studio remote connection article.

5. Security note

Enabling insecure guest logons and anonymous access reduces security and should only be used on an isolated, trusted LAN such as a classroom lab. For higher security, prefer named accounts with passwords and restrict share permissions appropriately.

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References:

• Can't access shared folders from File Explorer in Windows 10
• Error: Unable to connect to the machine <name>. The machine cannot be found on the network.
• The System Cannot a domain controller to service the authentication request. Please try again later - Microsoft Q&A