Qubit Finance Hack

TOTAL LOST $80.0M
High #93 All-Time Other

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain 2022 Incident surface
Recovered - No recovery reported
All-Time Rank #93 By amount stolen
Auditors 3 Prior security audits

Incident Overview

Quick Summary

Qubit Finance lending protocol was hacked due to smart contract vulnerability. The hacker minted $xETH tokens to steal 80,000,000 worth of $BNB

Details of the Exploit

Qubit Finance is DeFi protocol for lending and borrowing on both Ethereum and Binance SmartChain. The protocol confirmed a hack on Twitter, 206,809 $BNB was stolen which was worth 80,000,000 $USD up to that time. The attack flow is below:

The attacker:

- funded his wallet with 0.8887725 ETH from Tornado Cash

- sent 16 deposit transactions to QBridge of Ethereum

- sent 16 voteProposal transactions to QBridge contract of BSC by Qubit Relayer

- a number of $xETH tokens were minted by 16 voteProposal transactions, and liquidity in Qubit was withdrawn using this as collateral.

The attacker called the QBridge deposit function on the Ethereum network, which calls the deposit function QBridgeHandler. QBridgeHandler should receive the $WETH token, which is the original tokenAddress, and if the person who performed the tx does not have a $WETH token, the transfer should not occur.

tokenAddress.safeTransferFrom(depositer, address(this), amount);

In the deposit function above, tokenAddress is 0, so safeTransferFrom didn’t fail and the deposit function ended normally regardless of the amount value. Additionally, tokenAddress was the $WETH address before depositETH was added, but as depositETH is added, it is replaced with the zero address that is the tokenAddress of ETH.

In summary, the deposit function was a function that should not be used after depositETH was newly developed, but it remained in the contract, which allows the attacker to use this to steal the funds.

Block Data Reference

Attacker address:

https://etherscan.io/address/0xD01Ae1A7…1325c7

Incident Report

Protocol / Project Qubit Finance
Date of Incident
Attack Technique Other
Classification Borrowing and Lending
Primary Source View Post-Mortem

Protocol Information

Protocol Type Bridge
Official Website qbt.fi/app
Protocol Twitter/X @QubitFin
Team Anonymous
Source Code Unverified

Market Context at Time of Hack

Token Categories
Ethereum Ecosystem Yield Aggregator
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 other and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in Qubit Finance's contract logic - root cause: borrowing and lending
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 Other audit checklist and test coverage
Audited by Audit Report 1, Audit Report 2, Audit Report 3 — still lost $80.0M. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Qubit Finance, these are the critical security checks that could have prevented this incident (January 2022).

  • Verify all logic paths related to 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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Security Audit History

Sources & References

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