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

Attacker can reduce the amount of debt token minted to him

0xgh0st

Summary

When borrowers who have already taken a loan attempt to borrow additional debt tokens, the protocol issues them a balanceIncrease. However, the protocol currently determines whether a borrower is existing solely by checking their balanceOf() debt token balance. This check is insecure because attackers can manipulate their balance by transferring tokens to another wallet to falsely appear as a new borrower.

Vulnerability Details

  • The protocol initiates debt token minting by checking if a user is borrowing for the first time via their debt token balance balanceOf(onBehalfOf). However, this mechanism is flawed because attackers can transfer all their debt tokens to another wallet prior to borrowing again. This resets their balance to zero, allowing them to bypass borrower status checks and illegitimately receive first-time borrower benefits

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); <@ audit
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); <@ audit
}
​
_userState[onBehalfOf].index = index.toUint128();
​
uint256 amountToMint = amount + balanceIncrease; <@ audit
​
_mint(onBehalfOf, amountToMint.toUint128());
​
emit Transfer(address(0), onBehalfOf, amountToMint);
emit Mint(user, onBehalfOf, amountToMint, balanceIncrease, index);
​
return (scaledBalance == 0, amountToMint, totalSupply());
}

Impact

  • As a result, attackers can avoid incurring the balanceIncrease by transferring their debt tokens to another wallet, effectively resetting their balance and appearing as a new borrower.

Tools Used

Manual audit

Recommendations

The preferable method is to track user debt via a state variable instead of relying on token balances.

Updates

Lead Judging Commences

inallhonesty Lead Judge 4 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
inallhonesty Lead Judge 4 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement

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