Roughly Enough Items (REI) v.16.0.729 and before contains an Improper Validation of Specified Index, Position, or Offset in Input vulnerability. The specific issue is a failure to validate slot index and decrement stack count in the Roughly Enough Items (REI) mod for Minecraft, which allows in-game item duplication.
https://github.com/shedaniel/RoughlyEnoughItems/commit/e80ca84f1affb91d2388ddb298bfc6b141828cad
https://gist.github.com/apple502j/7b1af0082449c9bfbf910e9a25ef3595