When the great war ended in the Mahabharata, Kunti was the most
distressed. Although her sons (Pandavas) survived and emerged victorious, she
lost many near and dear ones including Karna, her eldest son. Death of Kunti
happened soon after. She along with Dhritarashtra and Gandhari took Vanaprastha
– they went to the forest to perform intense austerities.
Kunti died in forest fire. This is mentioned in the Ashramavasika
Parva of Mahabharata Chapter 36 – 37.