How much was lost in the Brinc Finance hack?

The Brinc Finance hack resulted in $1.1M in losses on December 14, 2021.

What attack technique was used in the Brinc Finance exploit?

The Brinc Finance exploit utilized Other. Understanding this attack vector is critical for smart contract auditors and developers building secure DeFi protocols.

How can developers prevent similar smart contract attacks?

Preventing smart contract hacks requires a combination of secure coding practices, thorough security audits, and understanding common attack vectors like reentrancy, oracle manipulation, and access control flaws. Smart Contract Hacking (SCH) provides hands-on training to help developers and auditors identify and prevent vulnerabilities before deployment.

Brinc Finance Hack

TOTAL LOST $1.1M

Medium Dec 14, 2021 Other

Affected Chain 2021 Incident surface

Recovered - No recovery reported

All-Time Rank #797 By amount stolen

Auditors 1 Prior security audit

Incident Overview

The address marked as "hacker" on Etherscan:

https://etherscan.io/address/0x6B0b6132…8f67Bb

1. The contract deployer of the staking contract invoked transferOwnership() at:

https://etherscan.io/tx/0x09ae252d…a00df4

2. The newOwner was set to "hacker's" address:

https://etherscan.io/address/0x6B0b6132…8f67Bb

3. The contract deployer of the staking contract upgraded implementation of the contract at:

https://etherscan.io/tx/0xdc7b9865…efcfa7

4. The new implementation is:

https://etherscan.io/address/0x1eC83036…bd8f3D#code

5. The new implementation includes rescueTokens() function which allows the owner to withdraw all tokens balance from the contract:

https://etherscan.io/address/0x1eC83036…bd8f3D#code#F1#L817

6. The "hacker" invokes rescueTokens() at:

https://etherscan.io/tx/0x729c2888…26da27

https://etherscan.io/tx/0x03bae1ef…c510db

7. The "hacker" burns BRC and receives DAI in exchange:

https://etherscan.io/tx/0x160471a4…da15bc

8. The "hacker" swaps gBRC for DAI on SushiSwap at:

https://etherscan.io/tx/0xfc559fad…e551f7

9. Stolen DAI were exchanged on ETH at:

https://etherscan.io/tx/0xc16be592…5fc9c9

10. Received ETH were deposited into Tornado Cash mixer at multiple transactions:

https://bloxy.info/txs/calls_from/0x6b0b6132…8f67bb?signature_id=994162&smart_contract_address_bin=0x722122df…5b6967

The hacker was funded by the contract deployer before the incident:

https://etherscan.io/tx/0xc95e14ea…0c4944

Incident Report

Protocol / Project Brinc Finance

Date of Incident December 14, 2021

Attack Technique Other

Classification Yield Aggregator

Primary Source View Post-Mortem

Protocol Information

Protocol Type Yield

Affected Token BRC, gBRC, sgBRC

Official Website brinc.fi/#/

Protocol Twitter/X @BrincFi

Team Anonymous

Source Code Unverified

Market Context at Time of Hack

Token Categories

Services DeFi Ethereum Ecosystem Lending & Borrowing BoostVC Portfolio Fenbushi Capital Portfolio Hashkey Capital Portfolio

Protocol Links

GitHub 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 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 Brinc Finance's contract logic - root cause: yield aggregator

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 — still lost $1.1M. Prior audits don't guarantee safety, especially after post-audit code changes.

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

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

Audit Report 1 Report

Sources & References

01
Source 1 https://twitter.com/BrincFi/status/1470592846009073664

Threat Assessment

Severity Level

MEDIUM

Attack Vector Other
Root Cause Yield Aggregator
Year 2021

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