NextGen - Deft_TT's results

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/main/smart-contracts/AuctionDemo.sol#L58 https://github.com/code-423n4/2023-10-nextgen/blob/main/smart-contracts/AuctionDemo.sol#L124 https://github.com/code-423n4/2023-10-nextgen/blob/main/smart-contracts/AuctionDemo.sol#L134

Vulnerability details

Impact

This will result in the NFT being auctioned off at a low price.

Proof of Concept

This vulnerability would allow a purchaser to undercut the price of an NFT, for example, at the very beginning of an auction, an attacker could use a very large amount of money to purchase the NFT, making it impossible for other bidders to bid on it because the bid price would need to be greater than the price offered by the last bidder "msg.value > returnHighestBid(_tokenid)". Because of the existence of cancelAllBids and cancelBid functions in the contract, it is already possible for the attacker to retrieve the funds for the bidding before the end, allowing another account of the attacker to buy it at a lower price.

Tools Used

none

Recommended Mitigation Steps

Prohibit users from withdrawing funds in auctions, suggest removing cancelAllBids and cancelBid functions

Assessed type

Other