Flash Loan

A flash loan is a DeFi innovation that allows users to borrow any amount of cryptocurrency without collateral, provided the loan is repaid within the same transaction. If the borrower cannot repay, the entire transaction reverts as if it never happened, eliminating default risk for the lender.

How Flash Loans Work:

1. User creates a transaction that borrows tokens from a flash loan pool
2. The borrowed funds are used for operations within the same transaction
3. At the end of the transaction, the loan plus a small fee must be repaid
4. If repayment fails, the entire transaction is rolled back (no funds lost)

Legitimate Use Cases: - Arbitrage: Exploiting price differences across DEXs in a single transaction - Collateral Swaps: Switching loan collateral without closing and reopening positions - Self-Liquidation: Repaying debt to avoid costly liquidation penalties - Governance Attacks: Temporarily acquiring voting power (controversial)

Flash Loan Providers:

Flash Loan Attacks: Flash loans have been used in numerous DeFi exploits. Attackers borrow large amounts to manipulate oracle prices, drain vulnerable pools, or exploit governance mechanisms. Notable attacks include bZx ($8M, 2020), Pancake Bunny ($45M, 2021), and Euler Finance ($197M, 2023).

Why They Matter: Flash loans democratize access to capital. Operations that previously required millions in upfront capital can now be executed by anyone who can write the smart contract logic, removing financial barriers to arbitrage and capital-efficient DeFi strategies.