Moonwell lost roughly $8.7 million on August 27. The response tells you how little room the team had left. Borrow caps on every Core Market on the Base network were set to 1 wei, the smallest unit the chain recognizes, which halts new borrowing across the entire deployment.
The three security firms that flagged the drain, CertiK, PeckShield and Blockaid, put the loss at $8.7 million within hours of each other. None of them pointed at a bug in Moonwell's code. The weak point was a price.
The collateral did the damage
MAMO is a thinly traded token listed as collateral inside Moonwell's lending market on Base. That thinness was the opening. The attacker pushed MAMO's collateral value up, then borrowed real assets against the inflated position, pulling 50.6 cbBTC worth more than $4 million out of the mCBTC market. The proceeds were funneled into DAI and parked at a single address.
| Detail | Figure |
|---|---|
| Reported loss | About $8.7 million |
| cbBTC borrowed out | 50.6, over $4 million |
| Borrow caps set to | 1 wei, all Base Core Markets |
| WELL price, 24 hours | Down about 13% |
| MAMO price, 24 hours | Down about 9% |
Why the fix looked so blunt
Setting a borrow cap to 1 wei is not a routine risk parameter. It is a kill switch. Moonwell applied it to all Core Markets on Base, not only the MAMO pool, and dropped supply caps for MAMO and WELL to the same floor. New borrowing across the network stopped cold. WELL, the protocol's governance token, fell about 13% over the following day. MAMO slid roughly 9%.
Not a smart-contract flaw
This is the kind of loss that does not surface when auditors read the contracts line by line. The math held. The inputs did not. It is a familiar shape: an illiquid token accepted as collateral, a price feed that trusts whatever that token last traded at, and an attacker with enough capital to shove a shallow pool. Coinliva has traced the same setup on other chains, from the exploit that wiped out BounceBit's vault to Rhea Finance's lending drain. It also cuts against a comfortable assumption, one worth reading against the finding that code bugs cause most crypto hacks but only a sliver of the losses. The money tends to leave through economic design, not broken syntax.
Moonwell has not said when Base borrowing reopens or whether affected suppliers will be made whole. The 1 wei caps stay in place until it does. For anyone lending on the chain, the thing to watch is whether those caps lift, and what MAMO is allowed to be worth when they do.
