Ethereum PoW, the Ethereum blockchain running on a proof-of-work (PoW) consensus mechanism, has faced a replay exploit.

According to the blockchain security company BlockSec, the attacker has successfully replayed call data from the PoS chain to the PoW chain (EthereumPoW).

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BlockSec claimed that the attack was executed through the Omni Bridge on the Gnosis chain. The attacker firstly used Omni Bridge to exploit 200  weighted ether (wETH) and then used the same message to grab 200 ETHW on the PoW chain. At that time, the approximate value of the theft was $1,600.

The firm noted that “the root cause of the exploitation is that the Omni bridge on the PoW chain uses the old chainID and doesn’t correctly verify the actual chainID of the cross-chain message,” highlighting that other protocols can also be prone to this problem.

On September 18th, the ETHW protocol developers confirmed the incident. However, the team claimed that it didn’t happen on the ETHW blockchain. The developers highlighted that the exploit affected only Omni bridge, while the Ethereum PoW network was not affected.

The ETHW developers noted that they have informed the Omni team about the exploit and emphasized that the “bridges need to correctly verify the actual ChainID of the cross-chain messages.”

In its blog post, while overviewing the exploit, the ETHW team said: 

ETHW itself has enforced EIP-155, and there is no replay attack from ETHPoS and to ETHPoS, which ETHW Core’s security engineers have planned in advance.

Following the exploit, the Ethereum PoW network saw glitches, resulting in users not being able to enter the blockchain’s servers while using the information provided by Ethereum PoW. Moreover, after the news about the exploit broke, ETHW’s price dropped by 37%, and at the time of writing ETHW, retails for $5.49. 

by Gile K. – Crypto Analyst, BitDegree