Core Contracts
Regnum Aurum Acquisition Corp
HardhatReal World AssetsNFT
77,280 USDC
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Submission Details
Severity: high
Invalid

Unused variable in repay function may cause extra burn

0xbc000

Summary

In the file contracts/core/pools/LendingPool/LendingPool.sol function repayOnBehalfand _repay

The variable scaledAmount is not used during DeptToken burn in line 418

This may cause extra DeptToken burned.

Vulnerable Details

Within _repay function, if a malicious user repay with amounts so much higher than its own userScaledDebt, the contract still asks the DeptToken contract to burn the amount Dept tokens.

This may cause incorrect number being burned

function _repay(uint256 amount, address onBehalfOf) internal {
if (amount == 0) revert InvalidAmount();
if (onBehalfOf == address(0)) revert AddressCannotBeZero();
​
UserData storage user = userData[onBehalfOf];
​
// Update reserve state before repayment
ReserveLibrary.updateReserveState(reserve, rateData);
​
// Calculate the user's debt (for the onBehalfOf address)
uint256 userDebt = IDebtToken(reserve.reserveDebtTokenAddress).balanceOf(onBehalfOf);
uint256 userScaledDebt = userDebt.rayDiv(reserve.usageIndex);
​
// If amount is greater than userDebt, cap it at userDebt
uint256 actualRepayAmount = amount > userScaledDebt ? userScaledDebt : amount;
​
uint256 scaledAmount = actualRepayAmount.rayDiv(reserve.usageIndex);
​
// Burn DebtTokens from the user whose debt is being repaid (onBehalfOf)
// is not actualRepayAmount because we want to allow paying extra dust and we will then cap there
(uint256 amountScaled, uint256 newTotalSupply, uint256 amountBurned, uint256 balanceIncrease) =
IDebtToken(reserve.reserveDebtTokenAddress).burn(onBehalfOf, amount, reserve.usageIndex);
// Transfer reserve assets from the caller (msg.sender) to the reserve
IERC20(reserve.reserveAssetAddress).safeTransferFrom(msg.sender, reserve.reserveRTokenAddress, amountScaled);
reserve.totalUsage = newTotalSupply;
user.scaledDebtBalance -= amountBurned;
// Update liquidity and interest rates
ReserveLibrary.updateInterestRatesAndLiquidity(reserve, rateData, amountScaled, 0);
​
emit Repay(msg.sender, onBehalfOf, actualRepayAmount);
}

Impact

This may cause incorrect/higher amount of DeptToken got burned

Tools Used

Manual review

Recommendations

Suggest using the actualRepayAmount + extra dust for the burn function.

Updates

Lead Judging Commences

inallhonesty Lead Judge 7 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

DebtToken::burn calculates balanceIncrease (interest) but never applies it, allowing borrowers to repay loans without paying accrued interest

Interest IS applied through the balanceOf() mechanism. The separate balanceIncrease calculation is redundant/wrong. Users pay full debt including interest via userBalance capping.

inallhonesty Lead Judge 7 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

DebtToken::burn calculates balanceIncrease (interest) but never applies it, allowing borrowers to repay loans without paying accrued interest

Interest IS applied through the balanceOf() mechanism. The separate balanceIncrease calculation is redundant/wrong. Users pay full debt including interest via userBalance capping.

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