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

RToken's Mint Function Ignores Balance Increase During Additional Deposits

0xekkoo

Summary

The RToken contract correctly calculates balance increase from interest accrual during additional deposits but fails to include this increase in the final mint amount, leading to users receiving fewer RTokens than they should.

Vulnerability Details

In the mint function, the contract:

  1. Correctly calculates interest-accrued balance increase

  2. But fails to add this increase to the final mint amount

function mint(
address caller,
address onBehalfOf,
uint256 amountToMint,
uint256 index
) external override onlyReservePool returns (bool, uint256, uint256, uint256) {
if (amountToMint == 0) {
return (false, 0, 0, 0);
}
uint256 amountScaled = amountToMint.rayDiv(index);
if (amountScaled == 0) revert InvalidAmount();
​
uint256 scaledBalance = balanceOf(onBehalfOf);
bool isFirstMint = scaledBalance == 0;
// @audit - Correctly calculates balance increase
uint256 balanceIncrease = 0;
if (_userState[onBehalfOf].index != 0 && _userState[onBehalfOf].index < index) {
balanceIncrease = scaledBalance.rayMul(index) - scaledBalance.rayMul(_userState[onBehalfOf].index);
}
​
_userState[onBehalfOf].index = index.toUint128();
// @audit - But ignores balanceIncrease in final mint
_mint(onBehalfOf, amountToMint.toUint128());
​
emit Mint(caller, onBehalfOf, amountToMint, index);
​
return (isFirstMint, amountToMint, totalSupply(), amountScaled);
}

Impact

Users receive fewer RTokens than entitled during additional deposits as the contract fails to account for accrued interest in the mint amount, resulting in permanent loss of interest-accrued tokens.

Tools Used

  • Manual Review

Recommendations

Include the calculated balance increase when minting new tokens

Updates

Lead Judging Commences

inallhonesty Lead Judge about 2 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

RToken::mint calculates balanceIncrease (interest accrued since last interaction) but never mints it, causing users to lose earned interest between deposits

The balanceIncrease is the interest that has already accrued on the user's existing scaledBalance since their last interaction. It's not something you mint as new tokens in the _mint function.

inallhonesty Lead Judge about 2 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

RToken::mint calculates balanceIncrease (interest accrued since last interaction) but never mints it, causing users to lose earned interest between deposits

The balanceIncrease is the interest that has already accrued on the user's existing scaledBalance since their last interaction. It's not something you mint as new tokens in the _mint function.

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