Here are three specific DeFi smart contract vulnerabilities commonly identified in audit reports, presented with technical precision and remediation guidance. These examples reflect real-world attack vectors that have led to significant financial losses.
1. Reentrancy Vulnerability in Token Swaps
Description:
A reentrancy vulnerability occurs when a smart contract makes an external call to an untrusted contract (e.g., executing a token transfer) before updating its internal state. If the external contract is malicious, it can re-enter the vulnerable function multiple times within a single transaction, bypassing state checks and draining funds.
Specific Example:
In a DEX pair contract, the swap() function allows users to exchange tokens. The contract sends ETH to the user via user.transferETH(amount) before updating the pair’s reserve balances (reserveETH, reserveToken). A malicious user can deploy a contract that, upon receiving ETH, calls swap() again. Since the reserves
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