Balancer V2 Hack

TOTAL LOST $238K
Low Frontend Attack / Other ethereum

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain ethereum Incident surface
Recovered - No recovery reported
All-Time Rank #1234 By amount stolen
Auditors 1 Prior security audit

Incident Overview

Quick Summary

Balancer DEX faced a frontend vulnerability exploit on Sep 20, 2023, resulting in a loss of 238,000 USD.

Details of the Exploit

Balancer, an AMM-based DEX operating on multiple chains, experienced a frontend vulnerability exploit on September 20, 2023. The attacker managed to transfer the stolen funds using the bridge between the Avalanche and Ethereum chains. They also distributed some of the stolen funds to several wallets.

One of the attacker-related addresses, 0xf998, received 1.04 AVAX from MEXC.

Block Data Reference

The attacker's address:

- https://cchain.explorer.avax.network/address/0x645710af…088d7e

- https://cchain.explorer.avax.network/address/0xF99825f5…0a29D6

Funds Holders as of Sep 20, 2023:

- https://cchain.explorer.avax.network/address/0x645710af…088d7e

- https://cchain.explorer.avax.network/address/0x1c14D9cF…69294f

Bridging Transactions:

- https://cchain.explorer.avax.network/tx/0x3bee94d9…91597c

- https://cchain.explorer.avax.network/tx/0x129938d7…a57e4c

Incident Report

Protocol / Project Balancer V2
Date of Incident
Affected Chain(s) ethereum
Attack Technique Frontend Attack / Other
Classification Protocol Logic / Exchange (DEX)
Primary Source View Post-Mortem

Protocol Information

Protocol Type Dexs
Official Website balancer.fi/
Protocol Twitter/X @Balancer
Team Anonymous
Source Code Unverified

Market Context at Time of Hack

Token Categories
Decentralized Exchange (DEX) Token DeFi DAO Ethereum Ecosystem Yield Farming AMM Three Arrows Capital Portfolio Governance
Protocol Links
GitHub Discord

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.

Technical Knowledge Deep understanding of frontend attack / other and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with ethereum smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in Balancer V2's contract logic - root cause: protocol logic / exchange (dex)
Execution Speed Precise transaction ordering and timing including MEV-awareness for frontrunning
Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Frontend Attack / Other audit checklist and test coverage
Audited by Audit Report 1 — still lost $238K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Balancer V2, these are the critical security checks that could have prevented this incident (September 2023).

  • Verify all logic paths related to Frontend Attack / 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

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Security Audit History

Sources & References

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