The bug

Many exploding tnt minecarts and / or ender crystals can cause a StackOverflowError. The reason for this is that they, unlike tnt, explode instantaneously even if they are ignited by other explosions. This means when one tnt minecart or ender crystal explodes, the explosion deals damage to the next tnt minecart or ender crystal causing it to explode as well and so on.

How to reproduce

1. Place a tnt minecart
2. Duplicate the amount of tnt minecarts up to about 2048 (number can be seen on the debug screen (F3) next to "E:")

   /execute @e[type=tnt_minecart] ~ ~ ~ summon tnt_minecart
   

3. Cause one tnt minecart to explode

   /entitydata @e[type=tnt_minecart,c=1] {TNTFuse:0}