Submitted by gpersoon, also found by elprofesor, fr0zn, and pauliax
Suppose someone claims the last part of his airdrop via claimExact() of AirdropDistribution.sol
Then airdrop\[msg.sender].amount will be set to 0.
Suppose you then call validate() again.
The check airdrop\[msg.sender].amount == 0 will allow you to continue, because amount has just be set to 0.
In the next part of the function, airdrop\[msg.sender] is overwritten with fresh values and airdrop\[msg.sender].claimed will be reset to 0.
Now you can claim your airdrop again (as long as there are tokens present in the contract)
Note: The function claim() prevents this from happening via assert(airdrop\[msg.sender].amount - claimable != 0);, which has its own problems, see other reported issues.
// https://github.com/code-423n4/2021-11-bootfinance/blob/7c457b2b5ba6b2c887dafdf7428fd577e405d652/vesting/contracts/AirdropDistribution.sol#L555-L563
// https://github.com/code-423n4/2021-11-bootfinance/blob/7c457b2b5ba6b2c887dafdf7428fd577e405d652/vesting/contracts/AirdropDistribution.sol#L504-L517
Add the following to validate() : require(validated\[msg.sender]== 0, "Already validated.");
chickenpie347 (Boot Finance) confirmed and resolved:
