It is difficult to see enough detail, but it looks similar to another posting. Spiraea alba var. latifolia
It has opposite leaves, so it isn't Spiraea (which has spirally arranged leaves). Not sure what it is, though.
The photo isn't very clear, but try comparing to Veronicastrum sp. such as V. virginicum (which does have opposite leaves)...(although I would prefer the flower spikes to be pointier for veronicastrum).