What happens if the stock runs out in canasta?

In the card game of canasta, the stock rarely runs out before a player goes out. If the final card drawn from the stock is a red 3, the game ends immediately, though the player may meld or lay off cards before the hand concludes without a discard.1

If the last card drawn is not a red 3, play continues without a stock. In this phase, each player in turn must take the upcard from the discard pile if it can be legally melded or laid off. The turn then ends by discarding or melding out. This process continues until one player goes out or until a player is unable to use the previous player's discard, at which point all play ceases.1