Race condition in approve() 收件箱

[code423n4]

Handle

cccz

Vulnerability details

Impact

Using approve() to manage allowances opens yourself and users of the token up to frontrunning.

https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/edit#heading=h.b32yfk54vyg9

Proof of Concept

https://github.com/code-423n4/2021-12-nftx/blob/main/nftx-protocol-v2/contracts/solidity/token/ERC20Upgradeable.sol#L141-L144

Tools Used

Manual analysis

Recommended Mitigation Steps

function approve(address spender, uint256 amount) public virtual override returns (bool) {

• require((amount == 0) || (_allowances(_msgSender(), spender) == 0));
    _approve(_msgSender(), spender, amount);
    return true;
  

  }