For sure a failed heater control valve. The 2 nuts on the base are all that hold it on. There is a moulded gasket between the base and the heater core. The new valve will come with a new gasket. Take the hose connection loose and remove the 2 nuts. Take it off with the control cable still hooked up. Once it is off but still on the control cable, you can rotate the valve so as to be able to see the cable hook up. Make a mental note of where the cable attaches and how much inner wire is showing past the cable stop. If you get the relationship right, you can hook up the new valve on the control cable exactly the same way, before rotating the valve to it's correct position to re atttach the new valve to the heater core. After you get the valve secured to the heater core, play around with the control cable lever to make sure it is moving through it's range of motion properly before hooking up the hose and re-watering the system with anti freeze.
Chill is correct. Replace the hose at the same time you replace the valve. It is a shaped hose, so order a new hose at the same time you order the new valve.