AirDropper
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Submission Details
Severity: high
Valid

Deploy script uses wrong USDC token address causing claims to fail

r0p

Title: Deploy script uses wrong USDC token address causing claims to fail
Severity: High
Impact: Airdrop contract receives zero tokens — all 4 eligible users can never claim.
Likelihood: High — deterministic, hardcoded in deploy script, every deployment affected.
Reference Files: script/Deploy.s.sol:8,18

Description

The deploy script declares s_zkSyncUSDC for the zkSync USDC address but uses a different hardcoded address on the transfer line. The variable is ignored and the actual funding transfer goes to a potentially wrong address. The vulnerable code:

address public s_zkSyncUSDC = 0x1D17CbCf0D6d143135be902365d2e5E2a16538d4;
​
function run() public {
vm.startBroadcast();
MerkleAirdrop airdrop = deployMerkleDropper(s_merkleRoot, IERC20(s_zkSyncUSDC));
IERC20(0x1d17CBcF0D6D143135aE902365D2E5e2A16538D4).transfer(address(airdrop), s_amountToAirdrop);
// ^^^ different casing — potentially wrong address ^^^^^^^^ return value ignored
vm.stopBroadcast();
}

The airdrop contract is deployed with s_zkSyncUSDC, but tokens are transferred from a separately hardcoded address with different EIP-55 casing. The transfer() return value is ignored — a silent failure leaves the contract with zero tokens.

Risk

Impact: High. If the hardcoded address is incorrect or the deployer lacks sufficient balance, the transfer silently fails. The contract deploys with zero tokens and every claim attempt reverts with a transfer failure.
Likelihood: High. The address mismatch is hardcoded in the deploy script. The unchecked return value guarantees silent failure.
The deployer announces a successful airdrop, 4 users attempt to claim, and all revert — 100 USDC intended for the airdrop never reaches the contract.

Proof of Concept

function testDeployTransferFailsSilently() public {
vm.startBroadcast();
MerkleAirdrop airdrop = new MerkleAirdrop(merkleRoot, token);
bool success = token.transfer(address(airdrop), 100e6); // deployer only has 50e6
assertFalse(success); // transfer failed silently — no revert
vm.stopBroadcast();
assertEq(token.balanceOf(address(airdrop)), 0); // empty contract deployed
}

The deployment succeeds but the contract holds zero tokens — all claims revert with no deployment-time indication.

Recommended Mitigation

function run() public {
vm.startBroadcast();
MerkleAirdrop airdrop = deployMerkleDropper(s_merkleRoot, IERC20(s_zkSyncUSDC));
require(IERC20(s_zkSyncUSDC).transfer(address(airdrop), s_amountToAirdrop), "Transfer failed");
vm.stopBroadcast();
}

Using s_zkSyncUSDC consistently and wrapping the transfer in require ensures the deployment reverts if token funding fails, preventing an empty airdrop contract.

Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 1 day ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-01] Address of USDC token in `Deploy.s.sol` is wrong causing the claiming process to fail

## Description The `s_zkSyncUSDC` address in `Deploy.s.sol` is incorrectly set, leading to a failure in the claiming process. This error results in funds being stuck in the `MerkleAirdrop` contract due to the immutability of the token address. ## Impact All funds become permanently trapped in the `MerkleAirdrop` contract, rendering them inaccessible for claiming or transfer. **Proof of Concept:** To demonstrate the issue, a test contract can be added and executed using the following command: `forge test --zksync --rpc-url $RPC_ZKSYNC --mt testDeployOnZkSync` Use the RPC URL `https://mainnet.era.zksync.io` for testing. <details> <summary>Proof Of Code</summary> ```javascript // SPDX-License-Identifier: MIT pragma solidity 0.8.24; import { MerkleAirdrop, IERC20 } from "../src/MerkleAirdrop.sol"; import { Test, console2 } from "forge-std/Test.sol"; contract MerkleAirdropTest is Test { MerkleAirdrop public s_airdrop; uint256 s_amountToCollect = (25 * 1e6); // 25.000000 address s_collectorOne = 0x20F41376c713072937eb02Be70ee1eD0D639966C; bytes32 s_proofOne = 0x32cee63464b09930b5c3f59f955c86694a4c640a03aa57e6f743d8a3ca5c8838; bytes32 s_proofTwo = 0x8ff683185668cbe035a18fccec4080d7a0331bb1bbc532324f40501de5e8ea5c; bytes32[] s_proof = [s_proofOne, s_proofTwo]; address public deployer; // From Deploy.t.sol bytes32 public s_merkleRoot = 0x3b2e22da63ae414086bec9c9da6b685f790c6fab200c7918f2879f08793d77bd; address public s_zkSyncUSDC = 0x1d17CBcF0D6D143135aE902365D2E5e2A16538D4; uint256 public s_amountToAirdrop = 4 * (25 * 1e6); function setUp() public { deployer = makeAddr("deployer"); deal(0x1D17CbCf0D6d143135be902365d2e5E2a16538d4, deployer, 100 * 1e6); vm.deal(s_collectorOne, 100 ether); } function testDeployOnZkSync() public { if (block.chainid != 324) { return; } vm.startPrank(deployer); // From here there is the code from run() s_airdrop = deployMerkleDropper(s_merkleRoot, IERC20(s_zkSyncUSDC)); // Send USDC -> Merkle Air Dropper IERC20(0x1d17CBcF0D6D143135aE902365D2E5e2A16538D4).transfer(address(s_airdrop), s_amountToAirdrop); // end code from run vm.stopPrank(); vm.startPrank(s_collectorOne); s_airdrop.claim{ value: s_airdrop.getFee() }(s_collectorOne, s_amountToCollect, s_proof); vm.stopPrank(); } function deployMerkleDropper(bytes32 merkleRoot, IERC20 zkSyncUSDC) public returns (MerkleAirdrop) { return (new MerkleAirdrop(merkleRoot, zkSyncUSDC)); } } ``` </details> ## Recommendations To resolve the issue, update the s_zkSyncUSDC address in Deploy.s.sol to the correct value: ```diff - address public s_zkSyncUSDC = 0x1D17CbCf0D6d143135be902365d2e5E2a16538d4; + address public s_zkSyncUSDC = 0x1d17CBcF0D6D143135aE902365D2E5e2A16538D4; ```

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