Submission Details
Impact:
Likelihood:
Reentrancy in redeemMemorabilia
The redeemMemorabilia function likely includes a call to an external contract (e.g., for minting an ERC1155 NFT) before** **updating internal state. If an attacker can exploit this with a fallback function, they could reenter redeemMemorabilia and redeem more items than intended. This violates the integrity of the redemption system and could drain BEAT tokens or inflate the NFT supply
Risk
Likelihood
The function is publicly accessible.
External minting is commonly delegated to external contracts.
If state changes (e.g.,
currentItemId++,burn(), etc.) happen after the call, reentrancy is exploitable.
Impact
Attacker can redeem multiple NFTs for a single BEAT cost.
Tokenomics and user trust may be severely damaged.
Potential full depletion of redeemable inventory or BEAT reserves.
#This contract will call redeemMemorabilia() again via fallback before state is updated, if no reentrancy protection exists.
contract Attack {
IFestivalPass fp;
bool attacked = false;
function attack() external {
fp.redeemMemorabilia(1); // trigger first call
}
fallback() external {
if (!attacked) {
attacked = true;
fp.redeemMemorabilia(1); // reenter before state is updated
}
}
}
Recommended Mitigation
#Add a reentrancy guard and follow the Checks-Effects-Interactions pattern. Update all internal state before making external calls.
- function attendPerformance(uint256 performanceId) external {
- rewards[msg.sender] += calculateReward(performanceId);
- }
+ mapping(address => mapping(uint256 => bool)) public hasAttended;
+ function attendPerformance(uint256 performanceId) external {
+ require(!hasAttended[msg.sender][performanceId], "Already attended");
+ hasAttended[msg.sender][performanceId] = true;
+ rewards[msg.sender] += calculateReward(performanceId);
+ }
Rewards breakdown
nSLOC
234This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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