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

The `StabilityPool.liquidateBorrower()` Function Calculates `scaledUserDebt` Incorrectly

kupiasec

Summary

The StabilityPool.liquidateBorrower() function calculates scaledUserDebt by multiplying the debt index with the userDebt. However, userDebt already represents the exact user debt amount in the units of crvUSDToken, making the multiplication by the debt index unnecessary.

Vulnerability Details

The StabilityPool.liquidateBorrower() function calculates scaledUserDebt by multiplying the debt index with the userDebt. The userDebt is obtained from the lendingPool.getUserDebt() function, which accurately reflects the user's debt amount in crvUSDToken. Therefore, multiplying by the debt index is redundant.

As a result, when liquidating a borrower, more tokens are paid than necessary.

function liquidateBorrower(address userAddress) external onlyManagerOrOwner nonReentrant whenNotPaused {
_update();
// Get the user's debt from the LendingPool.
uint256 userDebt = lendingPool.getUserDebt(userAddress);
453 uint256 scaledUserDebt = WadRayMath.rayMul(userDebt, lendingPool.getNormalizedDebt());
​
if (userDebt == 0) revert InvalidAmount();
​
uint256 crvUSDBalance = crvUSDToken.balanceOf(address(this));
if (crvUSDBalance < scaledUserDebt) revert InsufficientBalance();
​
// Approve the LendingPool to transfer the debt amount
bool approveSuccess = crvUSDToken.approve(address(lendingPool), scaledUserDebt);
if (!approveSuccess) revert ApprovalFailed();
// Update lending pool state before liquidation
lendingPool.updateState();
​
// Call finalizeLiquidation on LendingPool
lendingPool.finalizeLiquidation(userAddress);
​
emit BorrowerLiquidated(userAddress, scaledUserDebt);
}

Impact

The liquidation process requires more tokens than it should.

Tools Used

Manual review

Recommendations

Use userDebt directly without multiplication.

function liquidateBorrower(address userAddress) external onlyManagerOrOwner nonReentrant whenNotPaused {
_update();
// Get the user's debt from the LendingPool.
uint256 userDebt = lendingPool.getUserDebt(userAddress);
- uint256 scaledUserDebt = WadRayMath.rayMul(userDebt, lendingPool.getNormalizedDebt());
+ uint256 scaledUserDebt = userDebt;
​
if (userDebt == 0) revert InvalidAmount();
​
uint256 crvUSDBalance = crvUSDToken.balanceOf(address(this));
if (crvUSDBalance < scaledUserDebt) revert InsufficientBalance();
​
// Approve the LendingPool to transfer the debt amount
bool approveSuccess = crvUSDToken.approve(address(lendingPool), scaledUserDebt);
if (!approveSuccess) revert ApprovalFailed();
// Update lending pool state before liquidation
lendingPool.updateState();
​
// Call finalizeLiquidation on LendingPool
lendingPool.finalizeLiquidation(userAddress);
​
emit BorrowerLiquidated(userAddress, scaledUserDebt);
}
Updates

Lead Judging Commences

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

StabilityPool::liquidateBorrower double-scales debt by multiplying already-scaled userDebt with usage index again, causing liquidations to fail

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