Thorchain DEX Hack

TOTAL LOST $5.0M
Medium Over-ride Logic Exploit / Other ethereum

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain ethereum Incident surface
Recovered - No recovery reported
All-Time Rank #425 By amount stolen
Auditors 1 Prior security audit

Incident Overview

THORChain Exploiter 1 Address: https://etherscan.io/address/0x4b713980…5ebc5a

THORChain Exploiter 2 Wallet: https://etherscan.io/address/0x3a196410…85c031

Contract attacker address:

https://etherscan.io/address/0x4a338620…8e3c9c

According to ThorChain’s preliminary incident report, the bug was located within the ETH Bifrost (bridge) code:

https://gitlab.com/thorchain/thornode/-/blob/develop/bifrost/pkg/chainclients/ethereum/ethereum_block_scanner.go#L794

The code contains an over-ride loop, designed only for use in vaultTransferEvent transactions, which the hacker was able to manipulate. The hacker was able to wrap the router with their own contract, allowing them to access this over-ride.

The attacker drained liquidity in various coins:

- 2,500 ETH

- 57,975.33 SUSHI

- 8.7365 YFI

- 171,912.96 DODO

- 514.519 ALCX

- 1,167,216.739 KYL

- 13.30 AAVE

Ether were sent to the external address:

https://etherscan.io/address/0xace2d948…bc470e

Incident Report

Protocol / Project Thorchain DEX
Date of Incident
Affected Chain(s) ethereum
Attack Technique Over-ride Logic Exploit / Other
Classification Protocol Logic / Exchange (DEX)
Primary Source View Post-Mortem

Protocol Information

Protocol Type Dexs
Affected Token RUNE
Smart Contract Language Solidity
Official Website thorchain.org/
Protocol Twitter/X @thorchain

Market Context at Time of Hack

Token Categories
Cosmos Ecosystem Decentralized Exchange (DEX) Token DeFi DEX Multicoin Capital Portfolio Exnetwork Capital Portfolio Injective Ecosystem THORChain Ecosystem
Protocol Links
GitHub Discord Reddit

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 over-ride logic exploit / 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 Thorchain DEX's contract logic - root cause: protocol logic / exchange (dex)
Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block
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 Over-ride Logic Exploit / Other audit checklist and test coverage
Audited by Certik — still lost $5.0M. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Thorchain DEX, these are the critical security checks that could have prevented this incident (July 2021).

  • Verify all logic paths related to Over-ride Logic 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

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Security Audit History

Sources & References

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