DeFi Smart Contract Vulnerabilities Audit Guide

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

1. Reentrancy Attacks

What it is:

A reentrancy vulnerability occurs when a smart contract makes an external call to another contract (e.g., sending ETH or tokens) and then updates its internal state after the external call. A malicious contract can "re-enter" the first contract during the external call, before the state is updated, allowing it to drain funds repeatedly.

How to Detect It:

• Static Analysis Tools: Use tools like Slither, Mythril, or Semgrep to flag patterns where call.value() or transfer() occurs before state variable updates. Slither, for example, has a specific detector for reentrancy-eth.
• Code Pattern Review: Look for the **Checks-Effects-Interactions (CEI