Axelar Network v2 contest - ashiq0x01's results

Lines of code

https://github.com/code-423n4/2022-07-axelar/blob/9c4c44b94cddbd48b9baae30051a4e13cbe39539/contracts/gas-service/AxelarGasService.sol#L128 https://github.com/code-423n4/2022-07-axelar/blob/9c4c44b94cddbd48b9baae30051a4e13cbe39539/contracts/gas-service/AxelarGasService.sol#L144

Vulnerability details

Impact

The use of payable.transfer() is heavily frowned upon because it can lead to the locking of funds. The transfer() call requires that the recipient has a payable callback, only provides 2300 gas for its operation. This means the following cases can cause the transfer to fail:

• The contract does not have a payable callback
• The contract’s payable callback spends more than 2300 gas (which is only enough to emit something)
• The contract is called through a proxy which itself uses up the 2300 gas

Proof of Concept

See the linked code snippets above.

Tools Used

none

Recommended Mitigation Steps

Replace transfer() calls with call(). Keep in mind to check whether the call was successful by validating the return value:

(bool success, ) = receiver.call{value: amount}("");
require(success, "Transfer failed.")