How much was lost in the Sanshu Inu hack?

The Sanshu Inu hack resulted in $280K in losses on July 21, 2021.

What attack technique was used in the Sanshu Inu exploit?

The Sanshu Inu 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.

Sanshu Inu Hack

TOTAL LOST $280K

Low Jul 21, 2021 Other

Affected Chain 2021 Incident surface

Recovered - No recovery reported

All-Time Rank #1172 By amount stolen

Protocol Type Exploit/Other Target category

Incident Overview

The attacker's address:

https://etherscan.io/address/0x0333e323…9f4fec

The affected Memstake contract:

https://etherscan.io/address/0x35c674c2…1c7810#code

The attacker:

- created two attack contracts, the first one deposited 2,049B KEANU:

https://etherscan.io/address/0x67a54b34…0d9dc3

the second one is the attack contract:

https://etherscan.io/address/0xe30dc9b3…3ad59f

- borrowed a large number of KEANU tokens using the flash loan from UniswapV2, and then deposited the tokens into/withdraws from the Memestake using the second smart contract. Since the KEANU has the deflation mechanism, which burns 2% tokens for each transaction, the real number of tokens deposited into the Memestake is smaller than the value (user.amount) maintained by the Memestake contract. The attacker repeated this process and made the number of KEANU tokens inside the Memestake decrease to a small one (1e-07):

https://etherscan.io/tx/0x00edd680…285808

- invoked the Memestake.updatePool() to update the accMfundPerShare. This value relies on the number of KEANU tokens (which was manipulated in the second step.) Then the attacker obtained a large number of Mfund(~61M):

https://etherscan.io/tx/0xa945b185…8dde41

- swapped the MFund and KEANU to WETH and deposited stolen funds into Tornado Cash mixer:

https://bloxy.info/txs/calls_from/0x0333e323…9f4fec?signature_id=994162&smart_contract_address_bin=0x722122df…5b6967

The attacker gained 156.51 ETH as profits.

Incident Report

Protocol / Project Sanshu Inu

Date of Incident July 21, 2021

Attack Technique Other

Classification Token

Primary Source View Post-Mortem #1 View Post-Mortem #2

Protocol Information

Protocol Type Exploit/Other

Affected Token SANSHU

Official Website sanshuinufinance.com/

Protocol Twitter/X @SanshuToken

Team Anonymous

Source Code Unverified

Market Context at Time of Hack

Token Categories

Solana Ecosystem

Protocol Links

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 Sanshu Inu's contract logic - root cause: token

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

If you're auditing a protocol with similar architecture to Sanshu Inu, these are the critical security checks that could have prevented this incident (July 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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Sources & References

01
Source 1 https://sanshu-inu.medium.com/woofdate-2-1-0-61eaa995f1be
02
Source 2 https://blocksecteam.medium.com/the-analysis-of-the-sanshu-inu-s…

Threat Assessment

Severity Level

LOW

Attack Vector Other
Root Cause Token
Year 2021

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