What happened
On December 28, 2024 an attacker drained BIZNESS tokens from the Locker contract of the Standing on Bizness (BIZNESS) token on Base through a reentrancy bug, a loss TenArmor put at about $15,700. The Locker's splitLock function sent surplus ETH back to the caller through _feeHandler before it reduced the original lock's amount. The attacker's contract re-entered withdrawLock during that ETH transfer and withdrew the full original lock, while splitLock then still created a new lock for almost the same amount. Basescan shows dozens of transfers of about 4.41 million BIZNESS each from the Locker to the attack contract in the single transaction. Quadriga Initiative found no acknowledgment of the exploit from the team.
Attacker: 0x3cc1edd8a25c912fcb51d7e61893e737c48cd98d
Attack contract: 0x0f30ae8f41a5d3cc96abd07adf1550a9a0e557b5
Attack tx: 0x984cb29cdb4e92e5899e9c94768f8a34047d0e1074f9c4109364e3682e488873
How it happened
- The attack contract was the beneficiary of a lock in the Locker (lock ID 11 in the DeFiHackLabs reproduction) holding BIZNESS tokens.
- It called
splitLockon that lock with a small ETH fee payment, asking for a new lock of almost the whole amount. splitLockcalled_feeHandler, which sent the surplus ETH back to the caller before the original lock's amount was reduced.- The attack contract's
receive()function re-enteredwithdrawLockon the original lock, which still showed the full amount, and withdrew those tokens. splitLockthen finished and created a new lock holding almost the same amount, so the tokens could be withdrawn again. The attacker repeated the cycle many times in the one transaction.
Protocol details
Evidence
- report TenArmor Security Alert: Reentrancy attack on #BIZNESS #Locker on #BASE x.com
- transaction Basescan transaction 0x984cb29c... basescan.org
- analysis DeFiLlama defillama.com
- analysis DeFiHackLabs Bizness_exp.sol raw.githubusercontent.com
- analysis Dec 2024 - Standing on Bizness (BIZNESS) SplitLock Reentrancy Attack (Quadriga Initiative) quadrigainitiative.com
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