Is kissing the foot of one's maternal aunt or paternal aunt forbidden? May Allah reward you with all goodness.

The maternal aunt (khālah) and the paternal aunt (ammah) are mahram to a man. There is no harm in kissing them on the forehead, head, hand, or foot, provided there is no fear of temptation (fitnah). However, it is preferable to avoid kissing them unless there is a need, such as their arrival from a journey or similar circumstances.