How much was lost in the Sturdy V1 hack?

The Sturdy V1 hack resulted in $770K in losses on June 12, 2023.

What attack technique was used in the Sturdy V1 exploit?

The Sturdy V1 exploit utilized Flashloan Reentrancy Attack. 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.

Sturdy V1 Hack

TOTAL LOST $770K

Low Jun 12, 2023 Flashloan Reentrancy Attack ethereum

Affected Chain ethereum Incident surface

Recovered - No recovery reported

All-Time Rank #894 By amount stolen

Auditors 1 Prior security audit

Incident Overview

Sturdy is a first of its kind DeFi protocol for interest-free borrowing and high yield lending. Rather than charging borrowers interest, Sturdy stakes their collateral and passes the yield to lenders. This model changes the relationship between borrowers and lenders to make Sturdy the first positive-sum lending protocol.

This is classified as a Flash Loans Attacks, Reentrancy . Compare similar hacks →

Incident Report

Protocol / Project Sturdy V1

Date of Incident June 12, 2023

Affected Chain(s) ethereum

Attack Technique Flashloan Reentrancy Attack

Classification Ecosystem

Primary Source View Post-Mortem

Protocol Information

Protocol Type Lending

Smart Contract Language Solidity

Official Website app.sturdy.finance

Protocol Twitter/X @SturdyFinance

Market Context at Time of Hack

Token Categories

AI & Big Data Bittensor Ecosystem

Protocol Links

GitHub

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 flashloan reentrancy attack 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 Sturdy V1's contract logic - root cause: ecosystem

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? Yes — skilled auditors routinely flag Flashloan Reentrancy Attack vulnerabilities in code review

Audited by Audit Report 1 — still lost $770K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Sturdy V1, these are the critical security checks that could have prevented this incident (June 2023).

Verify all logic paths related to Flashloan Reentrancy Attack are guarded by proper access controls and input validation - see the Flash Loans Attacks attack class for patterns
Check that all state-changing functions follow the Checks-Effects-Interactions (CEI) pattern to prevent reentrancy and logic ordering bugs
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

Related Attack Classes

The technique used in this hack maps to these vulnerability classes in our security curriculum:

See all Flash Loans Attacks examples →

Flash Loans Attacks Reentrancy

Proof-of-Concept Exploits

1 PoC available

poc-exploits - sturdy v1

$ Sturdy Finance Read-Only-Reentrancy

On-Chain Evidence & References

Post-Mortem https://sturdyfinance.medium.com/exploit-post-mortem-49261493307a
Twitter/X Alert https://twitter.com/AnciliaInc/status/1668081008615325698
Twitter/X Alert https://twitter.com/BlockSecTeam/status/1668084629654638592

Sources & References

01
Source 1 https://twitter.com/blocksecteam/status/1668084629654638592

Threat Assessment

Severity Level

LOW

Attack Vector Flashloan Reentrancy Attack
Root Cause Ecosystem
Year 2023

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