Submitted by danb, also found by ACai, cmichel, harleythedog, leastwood, palina, pedroais, and WatchPug
totalUnderlying() includes the invested assets, they are not in the contract balance.
when a user calls withdraw, claimYield or unsponsor, the system might not have enough assets in the balance and the transfer would fail.
especially, force unsponsor will always fail, because it tries to transfer the entire totalUnderlying(), which the system doesnt have:
https://github.com/code-423n4/2022-01-sandclock/blob/main/sandclock/contracts/Vault.sol#L391
when the system doesnt have enough balance to make the transfer, withdraw from the strategy.
gabrielpoca (Sandclock) confirmed:
dmvt (judge) changed severity and commented:
