Lines of code

https://github.com/code-423n4/2023-05-venus/blob/main/contracts/VToken.sol#L946

Vulnerability details

Impact

File: VToken.sol
 946         uint256 repayAmountFinal = repayAmount > accountBorrowsPrev ? accountBorrowsPrev : repayAmount;
--skip--
 958         uint256 actualRepayAmount = _doTransferIn(payer, repayAmountFinal);

repayAmount is not allowed to exceed accountBorrowsPrev, which leads to the fact that if the UnderlyingToken has transaction fees, some debts will never be repaid. Cause the user to never be able to call exitMarket

Proof of Concept

Tools Used

manual

Recommended Mitigation Steps

It is recommended to allow repayAmount to exceed accountBorrowsPrev to cover transaction fees

Assessed type

DoS

code-423n4 / 2023-05-venus-findings

`VToken.sol#_repayBorrowFresh` If the UnderlyingToken requires transaction fees, there will always be some debt remaining #449