Heat the coconut oil in a deep pot over medium-high heat. Stir in the onions and garlic; cook until the onions are translucent, about 5 minutes. Mix in the vegetable broth, curry powder, salt, coriander, and red pepper flakes. Cook and stir until the mixture comes to a gentle boil, about 10 minutes. Cover, and boil 15 to 20 minutes more, stirring occasionally. Whisk in the pumpkin and coconut milk, and cook another 5 minutes.
Pour the soup into a blender, filling only half way and working in batches if necessary; process until smooth. Return to a pot, and reheat briefly over medium heat before serving.