Submitted by ronnyx2017, also found by cccz
https://github.com/code-423n4/2022-11-stakehouse/blob/main/contracts/liquid-staking/GiantPoolBase.sol#L57-L60
https://github.com/code-423n4/2022-11-stakehouse/blob/main/contracts/liquid-staking/GiantMevAndFeesPool.sol#L176-L178
https://github.com/code-423n4/2022-11-stakehouse/blob/main/contracts/liquid-staking/SyndicateRewardsProcessor.sol#L76-L90
The contract GiantMevAndFeesPool override the function totalRewardsReceived:
The function totalRewardsReceived is used as the current rewards balance to caculate the unprocessed rewards in the function SyndicateRewardsProcessor._updateAccumulatedETHPerLP
But it will decrease the idleETH first and then burn the lpTokenETH in the function GiantMevAndFeesPool.withdrawETH. The lpTokenETH burn option will trigger GiantMevAndFeesPool.beforeTokenTransfer which will call _updateAccumulatedETHPerLP and send the accumulated rewards to the msg sender. Because of the diminution of the idleETH, the accumulatedETHPerLPShare is added out of thin air. So the attacker can steal more eth from the GiantMevAndFeesPool.
I wrote a test file for proof, but there is another bug/vulnerability which will make the GiantMevAndFeesPool.withdrawETH function break down. I submitted it as the other finding named GiantLP with a transferHookProcessor cant be burned, users funds will be stuck in the Giant Pool. You should fix it first by modifying the code https://github.com/code-423n4/2022-11-stakehouse/blob/main/contracts/liquid-staking/GiantMevAndFeesPool.sol#L161-L166 to :
I know modifying the project source code is controversial. Please believe me its a bug needed to be fixed and its independent of the current vulnerability.
test:
test/foundry/TakeFromGiantPools2.t.sol
run test:
test log:
The attacker stole 2 eth from the pool.
foundry
idleETH -= _amount; should be after the lpTokenETH.burn.
vince0656 (Stakehouse) confirmed
