DeFi Smart Contract Vulnerabilities Audit Guide

Here are three of the most common DeFi smart contract vulnerabilities, along with specific detection methods used by security auditors and automated tools.

1. Reentrancy Attacks

What it is:

An attacker exploits a function that sends external calls (e.g., sending ETH or tokens) before the internal state variables are updated. By repeatedly calling the vulnerable function, the attacker can drain funds before the contract’s state reflects the actual balance changes.

Specific Detection Methods:

• State Variable Check Before External Call (CEI Pattern Violation): Use static analysis tools (e.g., Mythril, Slither, Echidna) to flag functions where an external call (call.value(), transfer(), or low-level call) occurs before any state variable (e.g., balances[addr], totalSupply) is updated. Example flag:

solidity
  // VULNERABLE