That pretty much has to be Amphicarpaea bracteata (Hog Peanut). It is a native species and one of the most common and abundant woodland legumes in the Missouri. Populations of this species often become quite dense along rocky slopes in heavily shaded moist ravines and floodplains. This is especially true if the woods have significant past disturbance. That being said, it is nothing to worry about. It is merely fulfilling its ecological role. It will decrease over the years as ecological succession proceeds.

Hog Peanut is so called because, like the true peanut, it produces below-ground fruits (as well as above-ground fruits). These small legumes were eaten by Native Americans. Settlers would turn their hogs loose in the woods to forage on said nuts. A practice that resulted in the negative impact of countless acres of forest.

Hope this helps.

Justin