DeFi Smart Contract Vulnerabilities Audit Guide

Here are three specific DeFi smart contract vulnerabilities commonly identified in audit reports, described with technical precision suitable for a professional security assessment.

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1. Reentrancy Attack (CEI Violation)

Description:

This vulnerability occurs when a smart contract calls an external contract (e.g., a DEX or another protocol) before updating its own internal state (e.g., user balances). If the external contract is malicious or compromised, it can re-enter the vulnerable function before the state update completes, allowing an attacker to repeatedly invoke the function and drain funds.

Specific Technical Scenario:

• A lending protocol’s withdraw(uint256 amount) function sends ETH to the user via call{value: amount}(user) before updating balances[user] -= amount.
• If the user address is an attacker-controlled contract, its receive() or fallback() function can recursively call withdraw() again.
• Since `balances