Lybra Finance - Breeje's results

Lines of code

https://github.com/code-423n4/2023-06-lybra/blob/main/contracts/lybra/configuration/LybraConfigurator.sol#L303

Vulnerability details

Impact

Freezing of distribution of rewards.

Proof of Concept

As per curve docs here, exchange_underlying call perform an exchange between two underlying coins.

Here, it's 4 parameters are:

• i: Index value of the underlying token to send.
• j: Index value of the underlying token to receive.
• dx: The amount of i being exchanged.
• min_dy: The minimum amount of j to receive. If the swap would result in less, the transaction will revert.

It is important to note that for last parameter, if swap output is less than that number, the transaction will revert.

File: LybraConfiguration.sol

303:    uint256 amount = curvePool.exchange_underlying(0, 2, balance, balance * price * 998 / 1e21);

Link to code

The code sets a very small slippage of 0.2%. While this may protect users from losing funds due to slippage, but during times of high volatility when slippage is unavoidable it will also cause this function of distributeRewards to always revert, leading to freezing funds. If a project uses a default slippage, there should always be a way to override this slippage with an external parameter to ensure that this transaction can go through even during times of high volatility.

Tools Used

VS Code

Recommended Mitigation Steps

Do not have a hardcoded Slippage.

Assessed type

DoS