Summary

It is a good idea to add a require() statement that checks the return value of ERC20 token transfers or to use something like OpenZeppelin’s safeTransfer()/safeTransferFrom() unless one is sure the given token reverts in case of a failure. Failure to do so will cause silent failures of transfers and affect token accounting in contract.

However, using require() to check transfer return values could lead to issues with non-compliant ERC20 tokens which do not return a boolean value. Therefore, it's highly advised to use OpenZeppelin’s safeTransfer()/safeTransferFrom().

Vulnerability Details

In line 157 of DSCEngine.sol

In line 274 of DSCEngine.sol

In line 285 of DSCEngine.sol

Impact

Tokens not compliant with the ERC20 specification could return false from the transfer function call to indicate the transfer fails, while the calling contract would not notice the failure if the return value is not checked. Checking the return value is a requirement, as written in the EIP-20 specification:

Tools Used

Manual Review

Recommendations

Use the SafeERC20 library implementation from OpenZeppelin and call safeTransfer or safeTransferFrom when transferring ERC20 tokens.