Is this overfitting?

Question

I have a CNN that is performing very well (96% accuracy, 1.~ loss) on training data but poorly (50% accuracy, 3.5 loss) on testing data.

Answer 1

96% accuracy suggests you have a really close fit to your training data. 50% accuracy on testing data shows that your model cannot account for the noise/variability of the data being studied. This looks like textbook overfitting.

You seem to be calling your validation data your test data. Maybe you can better partition your data?