Root + Impact

Description

Normal behavior:
Each Merkle proof (proof[]) must consist of a sequence of valid sibling hashes used to reconstruct the root from the leaf. These must be non-zero, properly computed, and match the tree depth.

Issue:
The final entry in output.json has this malformed proof:

• Two of the three sibling hashes are zeroed out.

• This either causes proof verification to fail or introduces a security hazard if 0-hashes are incorrectly treated as valid siblings in smart contract logic.

Risk

Likelihood: Medium

• This occurs due to a bug in the Merkle generation script where leaf indexing or tree filling fails to assign real sibling hashes.

• Since the script does not validate the structure or non-zero-ness of each proof[], this bug can silently propagate into production, where the proofs will fail on-chain verification or cause undefined behavior.

Impact: Medium

• The user 0xEa61F454C2B4A5A16AB556DBE8DBB176C1D02177 may be permanently blocked from claiming Snowman NFTs due to invalid proof generation.

• Other users and smart contracts relying on these proofs may incorrectly reject or validate claims.

• Airdrop credibility is undermined, as the proof file appears corrupted and unverified before use.

Proof of Concept

Affected record in output.json:

• Two invalid sibling hashes (0x0)

• This leaf will not reconstruct the Merkle root when passed through the standard verify() function.

• User will be unable to claim, and may never know why.

  The final Merkle proof entry includes zeroed-out siblings (0x000...) in the proof[] array. These are invalid and result from a logic bug during proof construction. The result is a broken Merkle proof, making the user's claim un-verifiable and invalid on-chain.

Recommended Mitigation

Before writing the final output.json, insert a check that:

• All proof[] values are non-zero

• All proofs match expected Merkle tree depth (e.g., 3 layers for 5 leaves → 3 siblings)

• Each generated proof successfully reconstructs the root when passed through MerkleProof.verify