Incident Overview
On September 2, 2025, Bunni DEX, a decentralized exchange built on Uniswap v4, suffered a multi-chain exploit that drained approximately $8.4 million in cryptocurrency. The attack targeted the BunniHub contract system with $2.3 million stolen on Ethereum and an additional ~$6.1 million from an earlier attack on Unichain, prompting the platform to pause all smart contract functions across networks.
The attacker exploited vulnerabilities in Bunni's custom Liquidity Distribution Function (LDF), which replaces Uniswap's standard logic to optimize returns for liquidity providers. By executing trades of very specific sizes, the exploiter manipulated the LDF curve and triggered faulty rebalancing calculations within the protocol's adaptive mechanisms. This caused the system to miscalculate liquidity provider share ownership, creating opportunities for gradual fund drainage.
The exploit specifically targeted how Bunni handles liquidity rebalancing across price ranges on its Uniswap v4-based infrastructure using the "hooks" feature. The attack occurred in two phases: an earlier exploit on Unichain network and a subsequent attack on Ethereum's mainnet targeting the BunniHub contract. Bunni's team immediately suspended all contract operations and urged users to withdraw funds while investigations continue.
Ethereum Exploit Transaction:
Unichain Exploit Transaction:
Attacker Wallets (Ethereum):
0xe04efd87…464f2b ($1.33M USDC, $1.04M USDT)
Incident Report
Protocol Information
What the Attacker Needed to Succeed
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Bunni V2, these are the critical security checks that could have prevented this incident (September 2025).
- Verify all logic paths related to Liquidity Distribution Function Exploit / Other are guarded by proper access controls and input validation
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.
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Sources & References
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