Is the story of Karna and Pitrupaksha mentioned in the Mahabharata directly?

The core narrative — Karnas arrival in Svarga and Indras explanation — is found in various Puranic elaborations of the Mahabharata tradition, particularly in the Brahma Vaivarta Purana. The Mahabharata itself in the Anushasana Parva provides extensive teachings on Shraddha through the broader doctrine of Pitru Rina.