A simple Solidity contract that entails a reentrancy attack vector.

Reentrancy.sol

// SPDX-License-Identifier: WTFPL
pragma solidity 0.8.19;

contract Victim {
    mapping(address => uint256) public balanceOf;

    function deposit() external payable {
        balanceOf[msg.sender] += msg.value;
    }

    function withdraw() external {
        uint256 depositedAmount = balanceOf[msg.sender];
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, ) = payable(msg.sender).call{value: depositedAmount}("");
        require(success, "Reverted");
        balanceOf[msg.sender] = 0;
    }
}