DeFi Smart Contract Vulnerabilities Audit Guide

Here are three critical DeFi smart contract vulnerabilities, along with specific detection methods used by security auditors and developers.

1. Reentrancy Attacks

Vulnerability Description:

Reentrancy occurs when a smart contract makes an external call (e.g., sending ETH to another address) before updating its own internal state. An attacker can exploit this by deploying a malicious contract that, upon receiving funds, recursively calls the vulnerable function again before the original function finishes execution. This can drain the contract’s balance.

How to Detect It:

• Code Pattern Analysis: Look for the pattern CEI (Checks-Effects-Interactions). If a contract performs external calls (.call, .transfer, .send) before updating state variables (e.g., balances[msg.sender] -= amount), it is vulnerable.
  • Example of Vulnerable Code:

solidity
    function withdraw(uint amount) public {