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DeFi Smart Contract Vulnerabilities Audit Guide

Here are three specific DeFi smart contract vulnerabilities commonly identified in professional security audits, detailed with technical context, impact, and remediation strategies.

1. Reentrancy Attack in Withdrawal/Claim Functions

Vulnerability Class: Reentrancy (CWE-841)

Likelihood: High if state updates occur after external calls.

Impact: Critical (Draining of contract funds).

Description

Reentrancy occurs when a contract makes an external call to an untrusted address before updating its internal state. If the external contract is malicious, it can re-enter the vulnerable function before the state change is recorded, allowing the attacker to repeatedly execute the same logic.

Example Scenario

A lending protocol allows users to withdraw their principal and interest. The vulnerable function withdraw() is structured as follows:


solidity
function withdraw() external {
    uint256 amount = balances[msg.sender];
    require(amount >
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