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

Incorrect return values in `burn()` function affect interest rate calculations

cipher27

Summary

The burn() function in RToken contract returns incorrect values which leads to wrong interest rate calculations in ReserveLibrary.

Vulnerability Details

The burn() function implementation shows incorrect return values:

/* @return A tuple containing:
* - uint256: The amount of scaled tokens burned
* - uint256: The new total supply after burning
* - uint256: The amount of underlying asset transferred
*/
function burn(
address from,
address receiverOfUnderlying,
uint256 amount,
uint256 index
) external override onlyReservePool returns (uint256, uint256, uint256) {
if (amount == 0) {
return (0, totalSupply(), 0);
}
​
uint256 userBalance = balanceOf(from);
​
_userState[from].index = index.toUint128();
​
if(amount > userBalance){
amount = userBalance;
}
​
uint256 amountScaled = amount.rayMul(index);
​
_userState[from].index = index.toUint128();
​
_burn(from, amount.toUint128());
​
if (receiverOfUnderlying != address(this)) {
IERC20(_assetAddress).safeTransfer(receiverOfUnderlying, amount);
}
​
emit Burn(from, receiverOfUnderlying, amount, index);
​
return (amount, totalSupply(), amount);
}

The third return value should be The amount of underlying asset transferred but it is returning the original amount.

So in the ReserveLibrary.withdraw() it will calculate the interest rate using the incorrect return value.

function withdraw(
ReserveData storage reserve,
ReserveRateData storage rateData,
uint256 amount,
address recipient
) internal returns (uint256 amountWithdrawn, uint256 amountScaled, uint256 amountUnderlying) {
if (amount < 1) revert InvalidAmount();
​
// Update the reserve interests
updateReserveInterests(reserve, rateData);
​
// Burn RToken from the recipient - will send underlying asset to the recipient
(uint256 burnedScaledAmount, uint256 newTotalSupply, uint256 amountUnderlying) = IRToken(reserve.reserveRTokenAddress).burn(
recipient, // from
recipient, // receiverOfUnderlying
amount, // amount
reserve.liquidityIndex // index
);
amountWithdrawn = burnedScaledAmount;
// Update the total liquidity and interest rates
updateInterestRatesAndLiquidity(reserve, rateData, 0, amountUnderlying);
​
emit Withdraw(recipient, amountUnderlying, burnedScaledAmount);
​
return (amountUnderlying, burnedScaledAmount, amountUnderlying);
}

Impact

The incorrect return values lead to wrong interest rate calculations in the lending pool after withdrawals.

Recommendations

Return amountScaled instead of amount as the third return value to ensure correct interest rate calculations.

Updates

Lead Judging Commences

inallhonesty Lead Judge 7 months ago
Submission Judgement Published
Validated
Assigned finding tags:

RToken::burn returns incorrect underlying asset amount (amount instead of amountScaled), leading to wrong interest rate calculations

inallhonesty Lead Judge 7 months ago
Submission Judgement Published
Validated
Assigned finding tags:

RToken::burn returns incorrect underlying asset amount (amount instead of amountScaled), leading to wrong interest rate calculations

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