Bid Beasts
First Flight #49
Beginner FriendlyFoundrySolidityNFT
100 EXP
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Submission Details
Severity: low
Valid

Unexpected NFT minimum price

febrian

BidBeastsNFTMarketPlace::placeBid comparison options make unexpected NFT minimum price

Description

This function is designed to allow bidders or buyers to submit their offers for acquiring the desired NFT, with the minimum bid price set at listing.minPrice—as established by the seller during the listing process.

However, a flaw in the comparison operator—using > (greater than) instead—forces bids to exceed listing.minPrice. This deviates from the protocol's documentation and the README.md file.

if (previousBidAmount == 0) {
​
requiredAmount = listing.minPrice;
@> require(msg.value > requiredAmount, "First bid must be > min price");
listing.auctionEnd = block.timestamp + S_AUCTION_EXTENSION_DURATION;
emit AuctionExtended(tokenId, listing.auctionEnd);
}

Risk

Likelihood: High

  • Reason 1: It's practically guaranteed that every prospective buyer will call this function to submit their bids.

  • Reason 2: The initial bidder or buyer will run into this particular code block.

Impact: Low

  • Impact 1: While it won't result in any financial losses, it nonetheless strays from the protocol's intended logic outlined in the documentation.

  • Impact 2: It compels the first bidder to submit an offer exceeding listing.minPrice.

Proof of Concept

This Foundry test returned true which mean expected revert has fulfilled.

function test_placeBid_unexpectedMinPrice() public {
_mintNFT();
_listNFT();
​
vm.prank(BIDDER_1);
vm.expectRevert("First bid must be > min price");
market.placeBid{value: MIN_PRICE}(TOKEN_ID);
}

Recommended Mitigation

Replace > with >= to allow bids equal to the minimum price.

if (previousBidAmount == 0) {
​
requiredAmount = listing.minPrice;
- require(msg.value > requiredAmount, "First bid must be > min price");
+ require(msg.value >= requiredAmount, "First bid must be >= min price");
listing.auctionEnd = block.timestamp + S_AUCTION_EXTENSION_DURATION;
emit AuctionExtended(tokenId, listing.auctionEnd);
}
Updates

Lead Judging Commences

cryptoghost Lead Judge 2 months ago
Submission Judgement Published
Validated
Assigned finding tags:

BidBeasts Marketplace: First Bid > Instead of >=

First bid validation uses > instead of >=, preventing valid starting bids.

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