Hi @Martin.Shemon ,
The NGFW will decrypt clientless VPN because it is designed to do so. The client creates an SSL session to the NGFW, and it creates a new SSL session to the internal server. This happens even if you do not have decryption enabled. It is, essentially, a man-in-the-middle.
You have 2 solutions, in my opinion.
Fix the decryption issue. For example, if you put the IP address in the Hostname field of the General tab and your certificate does not have the IP address in it, you will get decryption errors. Many times the issue will come down to supported and non-supported technologies. Please see the links below.
Use the GlobalProtect client. That traffic will abide by the decryption policy and can be excluded.
https://docs.paloaltonetworks.com/globalprotect/9-1/globalprotect-admin/globalprotect-clientless-vpn/supported-technologies
https://docs.paloaltonetworks.com/globalprotect/10-1/globalprotect-admin/globalprotect-clientless-vpn/supported-technologies
Thanks,
Tom
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