DeFi Smart Contract Vulnerabilities Audit Guide

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

1. Reentrancy Attacks

What it is:

Reoccurs when a smart contract calls an external contract (e.g., sending ETH or tokens) before updating its internal state. If the external contract is malicious, it can call back into the vulnerable function before the state update completes, allowing the attacker to drain funds repeatedly.

Example:

A withdraw() function sends ETH to the user before updating the user’s balance. The attacker’s contract receives the ETH and triggers a callback to withdraw() again before the balance is decremented.

How to Detect:

• Static Analysis: Use tools like Slither or SmartCheck to identify external calls (call, delegatecall, send) that occur before state variable updates. Look for patterns like:

solidity
  // Vulner