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How to Verify a Signature in a Wrong Way — The AssociationNFT Case

Code Auditing
April 21, 2022
Image: Raymond Clarke/Flickr
Image: Raymond Clarke/Flickr

The Association NFT is a NBA launched NFT. However, we find the NFT sale contract has a serious vulnerability which allows an attacker to mint a large number NFTs, without paying any Tokens.

The root cause of the vulnerability is the incorrect use of signature verification. Basically, the contract fails to ensure that the signature can only be used by the user (and only the user) once. In this case, the attacker can reuse a privileged user’s signature and mint tokens to him/herself.

We can see that in the verify function, there is no sender's address in the signature. Besides, there is no mechanism to include a nonce to ensure that the signature can only be used once. These security requirements are the basic knowledge in the software security class.

We are surprised that how such a vulnerability can exist in a popular NFT project. The whole community needs to pay more attention to the security of the contract.

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