Services not connecting to MQTT broker :

Hi

Since a recent update in our server (unclear to me which update did create the issue), the chirpstack components do not connect to the mosquitto broker anymore.
The error message is:

gateway/mqtt: connecting to mqtt broker failed, will retry in 2s: Network Error : x509: certificate relies on legacy Common Name field, use SANs or temporarily enable Common Name matching with GODEBUG=x509ignoreCN=0

Our configuration is based on a mosquitto server with self-signed certificate based access control. Running versions are:

mosquitto: Installed: 1.5.7-1+deb10u1
loraserver: Installed: 3.4.0
lora-gateway-bridge: Installed: 3.4.0
lora-app-server: Installed: 3.5.0

All other MQTT clients, each having its own certificate, can still connect and interact with the MQTT broker. Only the chirpstack components are failing.

My on-going investigations to solve this (regenerating certificates with SAN) have not been succesful up to now.
Any hints ?
Thank you