Handle

WatchPug

Vulnerability details

function _calcRewardIntegral(
    uint256 _index,
    address[2] memory _accounts,
    uint256[2] memory _balances,
    uint256 _supply,
    bool _isClaim
) internal {
    RewardType storage reward = rewards[_index];

    uint256 rewardIntegral = reward.reward_integral;
    uint256 rewardRemaining = reward.reward_remaining;

    //get difference in balance and remaining rewards
    //getReward is unguarded so we use reward_remaining to keep track of how much was actually claimed
    uint256 bal = IERC20(reward.reward_token).balanceOf(address(this));
    if (_supply > 0 && (bal - rewardRemaining) > 0) {
        rewardIntegral = uint128(rewardIntegral) + uint128(((bal - rewardRemaining) * 1e20) / _supply);
        reward.reward_integral = uint128(rewardIntegral);
    }

reward.reward_integral is uint128, if a early user mint (wrap) just 1 Wei of convexToken, and make _supply == 1, and then tranferring 5e18 of reward_token to the contract.

As a result, reward.reward_integral can exceed type(uint128).max and overflow, causing the rewards distribution to be disrupted.

Recommendation

Consider wrap a certain amount of initial totalSupply, e.g. 1e8, and never burn it. And consider using uint256 instead of uint128 for reward.reward_integral. Also, consdier lower 1e20 down to 1e12.

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