RebateFi Hook
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Beginner FriendlyDeFi
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Submission Details
Severity: low
Valid

Incorrect Fee Calculation in Event Emission (Logic Error + Misleading Data)

ashutoshcshah

Description:
In _beforeSwap, the fee amount for the ReFiSold event is calculated as:

uint256 feeAmount = (swapAmount * sellFee) / 100000;

Uniswap V4 fees are typically in pips (1/1,000,000). A fee of 3000 represents 0.3%.
The calculation uses a denominator of 100,000.
3000 / 100,000 = 0.03 = 3%.
The actual fee charged by the pool is 0.3%, but the event logs a fee of 3%.

Impact:

Off-chain indexers and users relying on events will see incorrect fee amounts (10x higher). This can lead to confusion, incorrect analytics, and accounting errors.

Proof of Concept:

function test_Bug_FeeEventCalculation() public {
// sellFee = 3000 (0.3%)
// Event emits: amount * 3000 / 100000 = 3%
uint256 expectedBuggyFee = (amountToSwap * 3000) / 100000;
vm.expectEmit(true, true, true, true);
emit ReFiSwapRebateHook.ReFiSold(address(swapRouter), amountToSwap, expectedBuggyFee);
// Trigger swap...
}

Recommended Mitigation:
Use the correct denominator (1,000,000) or LPFeeLibrary constants if available.

- uint256 feeAmount = (swapAmount * sellFee) / 100000;
+ uint256 feeAmount = (swapAmount * sellFee) / 1000000;
Updates

Lead Judging Commences

chaossr Lead Judge 11 days ago
Submission Judgement Published
Validated
Assigned finding tags:

Incorrect denominator (100000 instead of likely 1000000 or 10000) in fee calculation for ReFiSold event.

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