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Sablier
FoundryDeFi
20,000 USDC
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Submission Details
Severity: low
Invalid

fee amount is rounding down instead of rounding up

zukanopro

Vulnerability Details

Fee amount is calculated as below:

function calculateAmountsFromFee(
uint128 totalAmount,
UD60x18 fee
)
internal
pure
returns (uint128 feeAmount, uint128 netAmount)
{
// Calculate the fee amount based on the fee percentage.
feeAmount = ud(totalAmount).mul(fee).intoUint128(); // <---
​
// Calculate the net amount after subtracting the fee from the total amount.
netAmount = totalAmount - feeAmount;
}

mul()function: https://github.com/PaulRBerg/prb-math/blob/280fc5f77e1b21b9c54013aac51966be33f4a410/src/ud60x18/Math.sol#L450

function mul(UD60x18 x, UD60x18 y) pure returns (UD60x18 result) {
result = wrap(Common.mulDiv18(x.unwrap(), y.unwrap()));
}

From prb-math's dev note, function mulDiv18()is rounding down: https://github.com/PaulRBerg/prb-math/blob/280fc5f77e1b21b9c54013aac51966be33f4a410/src/Common.sol#L480

/// Notes:
/// - The body is purposely left uncommented; to understand how this works, see the documentation in {mulDiv}.
/// - The result is rounded toward zero.
/// - We take as an axiom that the result cannot be `MAX_UINT256` when x and y solve the following system of equations:

Rounding down fee can lead to negative impact, as it should always rounding down in every protocol

Impact

Financial problem

Tools Used

Manual review

Recommendations

feeAmountshould be rounding up.

Updates

Lead Judging Commences

inallhonesty Lead Judge 10 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity

Appeal created

zukanopro Submitter
10 months ago
inallhonesty Lead Judge
10 months ago
inallhonesty Lead Judge 10 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity

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