Ethereum's Achilles' Heel : Attacking and Fuzzing EVMs for FUN(and Profits)

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Presented at Zer0Con 2025 by

Bryton Bernard

Mathieu Hoste

Ethereum Virtual Machines (EVMs) are stack-based Turing-complete machines at the core of blockchain platforms like Ethereum, Aurora, and others. Ensuring their compliance and robustness is critical to blockchain security. This talk provides a deep dive into fuzzing techniques tailored for EVMs, focusing on harness-based fuzzing and differential fuzzing. Key highlights of the talk: Introduction to EVMs: - Overview of their architecture and functionality. - Use cases in popular implementations like Geth, Reth, Ethrex, and Aurora. Fuzzing Harnesses: - Examples of panic-inducing overflows in Rust-based EVMs. - Real-world examples of identified in Aurora and Ethrex. - Live demo showcasing how these bugs were identified and exploited. Differential Fuzzing: - Gas consumption differences between REVM and LEVM: Why inconsistencies in gas usage can lead to severe vulnerabilities. - Live demo of a gas-related vulnerability discovered in Ethrex. - Stack differential analysis: An explanation of its importance with a real-world example (no demo). - Memory differential analysis: How memory mismanagement can cause discrepancies and vulnerabilities across EVM implementations (example with non-compliance in the call opcode). Impact Analysis: - Focus on Denial-of-Service (DoS) attacks: Demonstrating how these vulnerabilities can lead to exploitation or even compromise the entire blockchain. This talk combines theoretical insights and practical demonstrations, making it a valuable resource for blockchain developers, researchers, and security professionals. Attendees will leave with a deeper understanding of EVM fuzzing, tools, and techniques for identifying and mitigating vulnerabilities.