Although this is not a major issue, there is the potential for a few problems. Moisture or pest intrusion is a possibility along with the loss of energy. In our northern climate where its cold in the winter, if moisture gets in there, it can freeze and crack the brick; and hot/humid in the summer months, moisture and pests can find their way through openings and into the home. Either way, any breaks in the building envelope will create a less energy efficient home. This is easily resolved by caulking around the pipe entering through the brick wall. Caulking should also be applied on the inside if accessible.