Windows 10 & 11: Security Policies Block Unauthenticated Guest Access - FIX!

Fixing SMB Guest Access Issues on Windows:

 Registry, Group Policy, and Server-Side

If you're trying to access an SMB share from Windows and getting blocked due to guest access restrictions, you're not alone. Microsoft tightened SMB security in recent versions of Windows, disabling insecure guest logons by default. While this improves security, it can break access to older or misconfigured servers — including setups like CasaOS or ZimaBoard.

Here are a few ways to fix it, ranging from quick registry tweaks to more secure server-side adjustments.