Lines of code

https://github.com/code-423n4/2023-04-caviar/blob/main/src/PrivatePool.sol#L661-#L687

Vulnerability details

Impact

Merkle tree have been found to be vulnerable to cross-chain-replay attacks. These attacks occur when an attacker replays transactions from one blockchain onto another blockchain that has a similar Merkle tree implementation, thereby tricking the victim into accepting forged data as legitimate.

The vulnerability arises due to the fact that Merkle trees are often constructed in a universal way that can be used across multiple blockchains. This approach, while increasing efficiency, can also create security risks.

Proof of Concept

If there's a fork, an attacker can monitor the blockchain for calls to operation to the protocol functionalities, and then make the same call with the same arguments on the other chain, which will send funds to the unsupported address.

Tools Used

Manual Review

Recommended Mitigation Steps

Enforce chain specific signature schemes to prevent from cross-chain replay attacks. Add a mechanism to allow tokens to be transferred to a different address using permit function from EIP-2612

code-423n4 / 2023-04-caviar-findings