Submission Details
Severity:
The user receives more debts than normal.
Summary
The user receives more debts than normal.
Vulnerability Details
DebtToken.sol#mint() function is as follows.
function mint(
address user,
address onBehalfOf,
uint256 amount,
uint256 index
) external override onlyReservePool returns (bool, uint256, uint256) {
if (user == address(0) || onBehalfOf == address(0)) revert InvalidAddress();
if (amount == 0) {
return (false, 0, totalSupply());
}
uint256 amountScaled = amount.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);
}
_userState[onBehalfOf].index = index.toUint128();
162@> uint256 amountToMint = amount + balanceIncrease;
_mint(onBehalfOf, amountToMint.toUint128());
emit Transfer(address(0), onBehalfOf, amountToMint);
emit Mint(user, onBehalfOf, amountToMint, balanceIncrease, index);
return (scaledBalance == 0, amountToMint, totalSupply());
}
DebtToken is rebasing token. But on L162, the protocol mints more amount than normal by adding increased amount by usageIndex.
This vulnerability leads to more debt to user.
Impact
This vulnerability leads to more debt to user.
Tools Used
Manual review
Recommendations
Modify DebtToken.sol#mint() function so that it only mints newly added debt amount.
Updates
Lead Judging Commences
inallhonesty 6 months ago
Submission Judgement Published Assigned finding tags:
DebtToken::mint miscalculates debt by applying interest twice, inflating borrow amounts and risking premature liquidations
Prize pool breakdown
Total prize
77,280 USDC
nSLOC
3,86420 USDC / LOC
74,000
3,280
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