In a large pot of boiling water, cook corn until warmed through, 3 to 5 minutes. Rinse with cold water until cool.
Meanwhile, combine tomatoes, onion, avocado, and basil in a large bowl. In a small bowl, combine remaining ingredients to make the vinaigrette, whisking until blended.
Cut corn kernels off cobs and add to salad, then pour in vinaigrette and toss gently to combine.