RebateFi Hook
First Flight #53
Beginner FriendlyDeFi
100 EXP
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Submission Details
Severity: low
Valid

Fee Calculation Denominator Mismatch in Event

objectplayer

Root + Impact

The feeAmount in ReFiSold event uses a 100,000 denominator while Uniswap V4 fees use 1,000,000 scale, causing the event to report 10x higher fees than actually charged.

Description

  • Uniswap V4 fees are expressed in hundredths of a basis point (1e-6), so sellFee=3000 means 0.3%.

  • The event calculation uses /100000, interpreting the same value as 3%.

// Root cause in RebateFiHook.sol line 166
} else {
fee = sellFee;
@> uint256 feeAmount = (swapAmount * sellFee) / 100000; // @> Should be /1000000
emit ReFiSold(sender, swapAmount, feeAmount);
}

Risk

Likelihood:

  • Occurs on every sell transaction

  • All off-chain analytics, dashboards, and integrations will show incorrect fee data

Impact:

  • Misleading fee information to users and integrators

  • Potential regulatory/compliance issues from inaccurate reporting

  • User confusion about actual costs

Proof of Concept

Let suppose if user wants to sale 1000 tokens and the sale fee is 0.3%, then 3 tokens will be charged but in current logic it is charging 3% (30 tokens) 10x the actual fee

// sellFee = 3000 (0.3% in Uniswap V4 scale)
// swapAmount = 1000 tokens
//
// Event reports: (1000 * 3000) / 100000 = 30 tokens (3%)
// Actual fee: (1000 * 3000) / 1000000 = 3 tokens (0.3%)
//
// Event shows 10x the actual fee

Recommended Mitigation

Use the correct denominator matching Uniswap V4's fee scale:

} else {
fee = sellFee;
- uint256 feeAmount = (swapAmount * sellFee) / 100000;
+ uint256 feeAmount = (swapAmount * sellFee) / 1000000;
emit ReFiSold(sender, swapAmount, feeAmount);
}
Updates

Lead Judging Commences

chaossr Lead Judge 12 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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