Hi Team Pen test reported that weak & invalid ssl communication is in use by one k3s server. Literally, i am a very new to this k3's. Could some one point me on how to fix the below issue

openssl s_client -connect kube1001:6443 2>&1 | grep issuer
verify error:num=20:unable to get local issuer certificate
issuer=/CN=k3s-server-ca@1649270763

openssl s_client -connect kube1001:443 2>&1 | grep issuer
verify error:num=20:unable to get local issuer certificate
issuer=/CN=k3s-server-ca@1649270763

openssl s_client -connect kube1001:80 2>&1 | grep issuer
verify error:num=20:unable to get local issuer certificate
issuer=/CN=k3s-server-ca@1649270763