Submission Details
Severity:
Users can burn in advance to avoid being liquidated
Summary
Users can burn in advance to avoid being liquidated
Vulnerability Details
As we can see ,the liquidate function will call _burnDsc to burn user's coin. If user infront run the burnDsc to burnDsc, It will cause liquidate error and revert.
function liquidate(address collateral, address user, uint256 debtToCover)
external
moreThanZero(debtToCover)
nonReentrant
{
// need to check health factor of the user
uint256 startingUserHealthFactor = _healthFactor(user);
if (startingUserHealthFactor >= MIN_HEALTH_FACTOR) {
revert DSCEngine__HealthFactorOk();
}
// We want to burn their DSC "debt"
// And take their collateral
// Bad User: $140 ETH, $100 DSC
// debtToCover = $100
// $100 of DSC == ??? ETH?
// 0.05 ETH
uint256 tokenAmountFromDebtCovered = getTokenAmountFromUsd(collateral, debtToCover);
// And give them a 10% bonus
// So we are giving the liquidator $110 of WETH for 100 DSC
// We should implement a feature to liquidate in the event the protocol is insolvent
// And sweep extra amounts into a treasury
// 0.05 * 0.1 = 0.005. Getting 0.055
uint256 bonusCollateral = (tokenAmountFromDebtCovered * LIQUIDATION_BONUS) / LIQUIDATION_PRECISION;
uint256 totalCollateralToRedeem = tokenAmountFromDebtCovered + bonusCollateral;
_redeemCollateral(user, msg.sender, collateral, totalCollateralToRedeem);
// We need to burn the DSC
_burnDsc(debtToCover, user, msg.sender);//@audit will burn user's coin
uint256 endingUserHealthFactor = _healthFactor(user);
if (endingUserHealthFactor <= startingUserHealthFactor) {
revert DSCEngine__HealthFactorNotImproved();
}
_revertIfHealthFactorIsBroken(msg.sender);
}
Impact
resulting in the user being unable to be liquidated
Tools Used
vs code
Recommendations
I think it's a design issue. We can check the remaining amount of the user's DecentralizedStableCoin, and cancel the burn in the liquidation function when the remaining amount is wrong
Prize pool breakdown
Total prize
15,000 USDC
nSLOC
23664 USDC / LOC
14,000 USDC
1,000 USDC
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