A Liveness Attack to Ethereum PoS with No Additional Cost

We present a liveness attack on the Ethereum PoS protocol, under which no blocks can be finalized. Our attack can be launched even when the network is synchronous and no validator is slashed (i.e., a slashed validator will eventually be removed from the system), which is the weakest assumption for any attack. Our experimental results using 16,384 validators on the latest Ethereum codebase validate our attack. To our knowledge, our attack is the first liveness attack that can be performed without manipulating the network or triggering the slashing condition, and has been experimentally validated.