DeFi Smart Contract Vulnerabilities Audit Guide

Here are three of the most common and impactful DeFi smart contract vulnerabilities, along with specific methods to detect them during code review or auditing.

1. Reentrancy

Description:

Reentrancy occurs when a smart contract calls an external contract (or a function within itself) before updating its own state. If the external contract is malicious or controlled by an attacker, it can re-enter the vulnerable function in the first call, executing it multiple times before the state is updated. This can drain funds, manipulate balances, or break invariants.

How to Detect It:

• Look for the "Check-Effects-Interactions" (CEI) pattern violation:
  • ✅ Safe: Check conditions → Update internal state (e.g., balance[msg.sender] -= amount) → Make external call (call.value(amount)).
  • ❌ Vulnerable: Check conditions → Make external call → Update internal state.
• **Static Analysis Tools