Udsen - CHECK THE ALLOWANCE AMOUNT BY THE `msg.sender` to `_spender` FOR THE GIVEN ERC20 TOKEN IS ZERO BEFORE CALLING THE `approve` FUNCTION

[github-actions[bot]]

Udsen

false

CHECK THE ALLOWANCE AMOUNT BY THE msg.sender to _spender FOR THE GIVEN ERC20 TOKEN IS ZERO BEFORE CALLING THE approve FUNCTION

Summary

It is recommended to check allowance from the msg.sender to the spender for the given erc20 token is zero before calling the token.approve() function.

Vulnerability Detail

Some ERC20 tokens such as usdt revert if the allowance > 0 when the approve function is called on the contract.

Impact

The transaction will revert if the allowance > 0, when approve function is called for ERC20 tokens such as usdt

Code Snippet

IERC20Upgradeable(token).approve(bank.cToken, amountCall);

https://github.com/sherlock-audit/2023-02-blueberry/blob/main/contracts/BlueBerryBank.sol#L882

Tool used

VS Code and Manual Review

Recommendation

It is recommended to check whether allowance > 0 for msg.sender to _spender before calling the approve function on the ERC20 token.