Incorrect Calculation of `amountScaled` in `RToken::burn` Function
Summary
Initializing amountScaled by Multiplying by index instead of dividing by it can lead to incorrect calculations.
Vulnerability Details
In the RToken::burn function, scaledAmount represents the amount of RToken that should be burned. It is intended to be calculated by dividing amount by reserve.liquidityIndex. However, in the current implementation, this calculation is incorrectly performed by multiplying amount by reserve.liquidityIndex (see here).
Additionally, following the same approach in the mint function, the burn function needs to define a variable called balanceIncrease and account for its effect on amountScaled.
Impact
This results in incorrect calculations.
Tools Used
Manual review
Recommendations
To correctly compute amountScaled when accounting for index and balanceIncrease, it should be calculated as follows:
This way, amountScaled should be burned instead of the original amount.
Lead Judging Commences
RToken::burn incorrectly calculates amountScaled using rayMul instead of rayDiv, causing incorrect token burn amounts and breaking the interest accrual mechanism
RToken::burn incorrectly calculates amountScaled using rayMul instead of rayDiv, causing incorrect token burn amounts and breaking the interest accrual mechanism
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