msgpackr is a fast MessagePack NodeJS/JavaScript implementation. Prior to 1.10.1, when decoding user supplied MessagePack messages, users can trigger stuck threads by crafting messages that keep the decoder stuck in a loop. The fix is available in v1.10.1. Exploits seem to require structured cloning, replacing the 0x70 extension with your own (that throws an error or does something other than recursive referencing) should mitigate the issue.
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.