EFLeverVault, a key component of Earning.Farm, was targeted with flash loan attacks on October 15, 2022. The contract failed to verify the origin of flashloan callbacks, allowing attackers to impersonate legitimate protocol calls and execute unauthorized ETH withdrawals from the collateral pool.

The EFLeverVault contract of Earning.Farm was attacked twice by flash loans. The first attack was intercepted by MEV bot, causing the contract to lose 480 ETH; the second hacker completed the attack, and the hacker made a profit of 268 ETH. After analysis, the vulnerability is caused by the contract’s flash loan callback function not verifying the flash loan initiator. The attacker can trigger the contract’s flash loan callback logic by itself: repay the Aave stETH debt in the contract and withdraw cash, and then exchange stETH for ETH. Then the attacker can call the withdraw function to withdraw the ETH balance in all contracts.