Snowman Merkle Airdrop
First Flight #42
Beginner FriendlyFoundrySolidityNFT
100 EXP
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Submission Details
Severity: low
Valid

Users can claim NFT multiple time

0xchaddb

Users can potentially claim multiple times due to missing duplicate claim validation in SnowmanAirdrop::claimSnowman

Description: The contract sets s_hasClaimedSnowman[receiver] = true but never checks this value before allowing claims, making the duplicate claim protection mapping pointless and potentially allowing users to claim multiple times.

function claimSnowman(/*...*/) external nonReentrant {
// ... validation ...
s_hasClaimedSnowman[receiver] = true; // Set but never checked
// ...
}

Impact: Potential double spending if duplicate claims are possible.

Recommended Mitigation: Add duplicate claim check before processing:

error SA__AlreadyClaimed();
​
function claimSnowman(address receiver, bytes32[] calldata merkleProof, uint8 v, bytes32 r, bytes32 s)
external nonReentrant {
if (receiver == address(0)) revert SA__ZeroAddress();
if (s_hasClaimedSnowman[receiver]) revert SA__AlreadyClaimed(); // ✅ Check before processing
if (i_snow.balanceOf(receiver) == 0) revert SA__ZeroAmount();
// ... rest of validation and processing ...
s_hasClaimedSnowman[receiver] = true;
emit SnowmanClaimedSuccessfully(receiver, amount);
i_snowman.mintSnowman(receiver, amount);
}
Updates

Lead Judging Commences

yeahchibyke Lead Judge 3 months ago
Submission Judgement Published
Validated
Assigned finding tags:

Lack of claim check

The claim function of the Snowman Airdrop contract doesn't check that a recipient has already claimed a Snowman. This poses no significant risk as is as farming period must have been long concluded before snapshot, creation of merkle script, and finally claiming.

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