Project

Summary

The upgradeTier function in the provided Solidity code does not check if the target tier still has available slots before minting a new user. This oversight can lead to over-allocation of memberships in a tier, causing potential inconsistencies and errors in the DAO’s membership management.
https://github.com/Cyfrin/2024-11-one-world/blob/main/contracts/dao/MembershipFactory.sol#L155-L160

Vulnerability Details

The vulnerability is due to the absence of a check to ensure that the target tier (fromTierIndex - 1) has available slots before minting a new user. The current code directly mints a new membership without verifying if the tier has reached its maximum capacity:

Without this check, the function can mint new memberships even if the tier is already full, leading to an over-subscription of the tier.

Impact

The lack of validation for available slots in the target tier can result in:

• Over-allocation of memberships, causing potential financial and operational discrepancies.

• Users being assigned to tiers that are already full, leading to unfair distribution and possible dissatisfaction among members.

• Inaccurate tracking of tier capacities, which can affect the overall management and governance of the DAO.

Tools Used

manual review

Recommendations

To fix the issue, add a check to ensure that the target tier has available slots before minting a new user. The updated code should include a validation similar to the following: