Banana Cake

1 (18.25 ounce) box Duncan Hines yellow cake mix
2 teaspoons vanilla extract
1/4 cup vegetable oil
3 eggs
3/4 cup milk
1 teaspoon baking soda
3 ripe bananas

Preheat oven to 350 degrees F. Lightly grease and flour a Bundt pan.

Mix all ingredients in a mixing bowl. Beat for at least 3 1/2 minutes. Pour into prepared pan, and bake for 45 minutes.