Critical temperature reached - don't shut down

From drivers/thermal/thermal_core.c:

    if (trip_type == THERMAL_TRIP_CRITICAL) {
             dev_emerg(&tz->device,
                       "critical temperature reached(%d C),shutting down\n",
                       tz->temperature / 1000);
             orderly_poweroff(true);
    }

So it seems it is not calling a script to handle the situation.

This is a really serious message. The computer only does this when there's a cooling problem. Under no circumstance the temperature should reach values this high. This immediate shutdown is an action triggered by the thermal sensor that operates independent of the operating system. It prevents the processor from getting damaged beyond repair. The bottomline is you can't prevent this protection measure and you should not ever want to do this if it had been possible. What you should do first now is checking what's wrong with cooling and solve the problem. I've experienced this problem a few years ago and it turned out to be the paste between the heatsink and the processor.