DeFi Smart Contract Vulnerabilities Audit Guide

Here are three of the most critical and common DeFi smart contract vulnerabilities, along with specific methods for detecting them.

1. Reentrancy Attacks

What it is:

Reentrancy occurs when a contract calls an external contract without ensuring that the state of the calling contract is fully updated. An attacker can exploit this by repeatedly calling the same function before the original call completes, allowing them to drain funds multiple times. The classic example is the 2016 The DAO hack.

How to Detect It:

• Look for the "CEI" Pattern Violation: Check if the contract follows the Checks-Effects-Interaction pattern. If an external call (e.g., address.transfer() or call()) happens before the state variables (like balances) are updated, it’s vulnerable.
  • ❌ Vulnerable:

solidity
    function withdraw(uint amount) external {
        require(b