Core Contracts

Summary

The function mint casts amountToMint to uint128 before passing it to OpenZeppelin's _mint function, which expects a uint256. This unnecessary and unsafe downcast could lead to unexpected overflows if amountToMint exceeds the maximum value of uint128. While toUint128() may work under normal conditions, any unforeseen increase in amountToMint beyond 2^128 - 1 would cause a silent truncation or error, leading to unexpected behavior.

Vulnerability Details

In the following line of code:

amountToMint is a uint256, and it is explicitly cast to uint128 before being passed to _mint, which is an OpenZeppelin function that accepts a uint256. This downcasting is unnecessary and introduces a risk of truncation if amountToMint exceeds 2^128 - 1.

Since the function takes an external input (amount) and adds balanceIncrease, ensuring that amountToMint never exceeds uint128 limits is crucial.

Impact

• If amountToMint exceeds uint128, the function could revert unexpectedly, disrupting operations.

• Potential for silent truncation, which could lead to minting an unintended amount of debt tokens.

• Limits the scalability of the contract unnecessarily.

• Introduces unnecessary complexity, as OpenZeppelin's _mint function already supports uint256.

Tools Used

• Manual code review

Recommendations

Remove the explicit casting to uint128 since OpenZeppelin's _mint function accepts a uint256.