What are the consequences of leaving the fridge door cracked open overnight?
If the food had reached a temperature of 21 C for an unknown amount of time, you should definitely discard it.

See:
How do I know if food left at room temperature is still safe to eat?



As a more general rule, there really is no way to provide a definitive answer; it depends on your specific refrigerator, the cooling power it has, how much air was able to move through the gap, and how much mass was inside the refrigerator to provide a thermal buffer   

If you had a refrigerator thermometer and looked at what temperature the interior rose to, if it was below 40 F you are good.

If you don't have a thermometer, you don't know exactly what happened inside.   

You must assess how much tolerance for risk you have.