Root: The contract performs an external token transfer call before updating internal state or protecting reentrancy.

Impact: A malicious token contract can re-enter the function before the state is consistent, leading to duplicated minting or state manipulation.

Description

• Normally, the function requestMintWeatherNFT registers a keeper and collects LINK tokens from the user using safeTransferFrom, then proceeds with other logic including requesting weather data and storing the mint request.

• However, if a malicious ERC20 token contract is used, it can reenter the same function or related logic during the safeTransferFrom call, because state updates or locks (like nonReentrant) are not applied yet.

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Risk

Likelihood:

• Attack surface opens when malicious tokens are used or in untrusted deployments.

• Commonly missed in test environments using mock ERC20s.

Impact:

• Double minting, corrupted accounting, or stuck LINK.

Proof of Concept: The MaliciousLINK token exploits the ERC20 transfer hook to re-enter the original requestMintWeatherNFT call during the safeTransferFrom, allowing attackers to bypass mint price increases, limits, or even mint multiple NFTs in one transaction.

Recommended Mitigation - This mitigation ensures that state changes occur before any external calls. Alternatively, applying a nonReentrant modifier to the function blocks recursive calls entirely. This defends against reentrancy by ensuring either:
(1) all internal state is locked before any external interaction, or
(2) the function can't be re-entered at all.