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

Incorrect Calculation of Minted Amount in RToken::mint Function

josh4324

Summary

The mint() function is responsible for minting tokens based on the scaled debt balance. However, it does not include balanceIncrease in the amountToMint before updating the index and minting the tokens. This means that accrued interest is not accounted for correctly, leading to incorrect token balances and potential loss of rewards.

Vulnerability Details

function mint(
address caller,
address onBehalfOf,
uint256 amountToMint,
uint256 index
) external override onlyReservePool returns (bool, uint256, uint256, uint256) {
if (amountToMint == 0) {
return (false, 0, 0, 0);
}
uint256 amountScaled = amountToMint.rayDiv(index);
​
if (amountScaled == 0) revert InvalidAmount();
​
uint256 scaledBalance = balanceOf(onBehalfOf);
bool isFirstMint = scaledBalance == 0;
​
uint256 balanceIncrease = 0;
if (_userState[onBehalfOf].index != 0 && _userState[onBehalfOf].index < index) {
balanceIncrease = scaledBalance.rayMul(index) - scaledBalance.rayMul(_userState[onBehalfOf].index);
}
// balanceIncrease not added to amountToMint
​
_userState[onBehalfOf].index = index.toUint128();
​
_mint(onBehalfOf, amountToMint.toUint128());
​
emit Mint(caller, onBehalfOf, amountToMint, index);
​
return (isFirstMint, amountToMint, totalSupply(), amountScaled);
}

The function calculates balanceIncrease, which represents the accumulated interest from the previous index to the new index. However, balanceIncrease is not added to amountToMint before updating the index and minting, this results in under-minting and incorrect reward calculations.

Impact

The system does not account for previously accrued interest when minting, leading to an incorrect balance.

Tools Used

Manual Review

Recommendations

Modify the _mint() function call to correctly account for accrued interest:

Updates

Lead Judging Commences

inallhonesty Lead Judge 3 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

RToken::mint calculates balanceIncrease (interest accrued since last interaction) but never mints it, causing users to lose earned interest between deposits

The balanceIncrease is the interest that has already accrued on the user's existing scaledBalance since their last interaction. It's not something you mint as new tokens in the _mint function.

inallhonesty Lead Judge 3 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

RToken::mint calculates balanceIncrease (interest accrued since last interaction) but never mints it, causing users to lose earned interest between deposits

The balanceIncrease is the interest that has already accrued on the user's existing scaledBalance since their last interaction. It's not something you mint as new tokens in the _mint function.

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