The funny thing is that the people in North Korea only survived due to capitalism. Because the government has been incapable of distributing food, people have been forced to obtain it by trading in ad-hoc black markets.
First, market socialism is socialism with elements from capitalism, so the particular mechanism (ad-hoc black markets) is a capitalist one, regardless of where it came from.
Second, in market socialism, the market is legal and "white". In North Korea, they are very much not legal - thus, "black".
Interestingly, the resilience of markets to pop up anywhere there's a need, regardless of legality or formal training in how to run them, tells us something about capitalism and it's inherent compatibility with human nature.