Take the leather item outside
Wear gloves and a mask
Brush off loose mold with a soft brush
Wipe the surface with a dry microfiber cloth
Mix equal parts white vinegar and water
Lightly dampen a cloth with the solution
Wipe the moldy areas gently
Do not soak the leather
Wipe again with a clean damp cloth
Dry the leather with a soft towel
Let it air-dry completely in a ventilated area
Keep it away from direct heat and sunlight
Apply a leather conditioner after drying
Repeat if mold remains
Store the leather in a cool, dry place