DeFi Smart Contract Vulnerabilities Audit Guide

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

1. Reentrancy

Vulnerability Description:
Reentrancy occurs when a smart contract calls an external contract (or itself) before updating its own state. If the external contract is malicious, it can re-enter the vulnerable function before the state change is complete, allowing the attacker to drain funds multiple times.

Specific Example:
A withdraw() function sends ETH to the user before updating the user’s balance in the contract’s internal mapping.

How to Detect It:

1. Static Analysis Tools:
   • Use tools like Slither (by Trail of Bits) or Mythril.
   • Look for the warning: reentrancy-eth or reentrancy-read.
   • Example Slither output: `Contract X has reentrancy: withdraw()