Crypto Gloss

Euler Finance

Euler Finance is a permissionless decentralized lending protocol that enables anyone to deploy isolated lending markets for any ERC-20 token without requiring governance approval. Unlike Aave and Compound, which support a curated whitelist of assets in a shared liquidity pool, Euler uses a vault-based architecture where each asset pair has its own isolated market — limiting contagion risk from volatile or obscure tokens while enabling lending for assets that would never clear a governance vote. Euler V1 launched in 2021 and reached ~$260M TVL before suffering a $197M flash loan exploit in March 2023 — one of DeFi’s largest hacks — from which it remarkably recovered most funds via negotiation. Euler V2 launched in 2024 with a redesigned architecture.

How It Works

Vault Architecture (V2):

In Euler V2, lending markets are Euler Vaults — isolated smart contracts, each representing a single-asset lending market:

  1. Vault Creation: Anyone can deploy a vault for any ERC-20 token without permission
  2. Vault Configuration: Creators set interest rate curves, LTV ratios, oracle sources, and borrow/collateral caps
  3. EVC (Ethereum Vault Connector): A shared middleware layer allows vaults to interoperate — enabling cross-vault strategies where collateral in one vault unlocks borrowing in another
  4. Lending: Depositors earn variable interest as the vault’s supply rate; borrowers pay the borrow rate
  5. Risk Isolation: A problem in one vault (bad oracle, insolvency) does not affect other vaults

Sub-Accounts:

  • Each Ethereum address has up to 256 sub-accounts on Euler
  • Sub-accounts allow managing separate collateral/borrow positions without clutter
  • Useful for hedging strategies, testing, or isolating liquidation risk

Interest Rate Model:

  • Reactive IRMs (Euler V2) — interest rates dynamically adjust based on utilization rate changes, not just the current utilization level. Rates accelerate faster when utilization enters a dangerous zone
  • Protocol parameter: rho controls how quickly the IRM reacts

V1 vs. V2:

Feature V1 V2
Architecture Shared pool + isolation tiers Full vault isolation
Permissionless Partial Full
Cross-vault No Yes (EVC)
Governance EUL token EUL token
Post-March 2023 Paused/deprecated Live

Key Features

Feature Detail
Permissionless vaults Anyone can create a market for any ERC-20
Risk isolation Each vault is isolated — no shared liquidity pool contagion
Sub-accounts 256 per address for position management
EVC Cross-vault collateral and borrowing coordination
Reactive IRM Dynamic interest rate response to utilization changes
Governance token EUL

Supported Chains

  • Ethereum (primary)
  • Arbitrum, Base, Optimism, Avalanche (V2 deployments)

History

  • 2021: Euler Finance founded by Michael Bentley; V1 protocol audited and launched on Ethereum
  • 2022: Rapid TVL growth to ~$260M; named one of the leading DeFi lending protocols
  • March 13, 2023: Flash loan exploit drains ~$197M via a donation attack + self-liquidation exploit — largest DeFi hack to that point in 2023
  • March–April 2023: Euler team negotiates with the attacker (white-hat framing claimed); 97% of funds returned — widely considered a remarkable recovery
  • 2024: Euler V2 launches with full vault isolation, EVC, and reactive IRM
  • 2024: Multi-chain expansion begins; V2 vaults deployed on Arbitrum, Base, and Optimism

Common Misconceptions

“Euler is just a clone of Aave.”

Euler’s permissionless vault architecture and risk isolation model differ fundamentally from Aave’s shared liquidity pool. The reactive IRM and sub-account system are also original designs not found in Aave V3.

“Euler collapsed after the 2023 hack.”

Most funds were returned. Euler V1 was deprecated but V2 launched with an architecturally redesigned system. The team and protocol continued operating.

Criticisms

  • V1 hack: Despite funds being returned, the $197M exploit—enabled by flawed collateral handling in self-liquidation — highlighted the risk of complex DeFi interactions in permissionless systems
  • EVC complexity: The cross-vault interaction layer adds composability but also attack surface — a single vault vulnerability can be escalated via EVC into adjacent vaults
  • Permissionless vault spam: Low barriers to market creation means some vaults may have manipulable oracles, thin liquidity, or intentionally misleading configurations

Social Media Sentiment

Euler Finance occupies a respected but niche position in DeFi — more trusted by technical users than mainstream depositors due to its hack history. Michael Bentley’s active technical communication and the recovered funds improved the protocol’s reputation significantly post-hack. DeFi researchers frequently cite Euler V2’s vault architecture as state-of-the-art permissionless lending design. EUL token trading volume has been moderate; the protocol remains more respected for its technical innovation than speculation.

Last updated: 2026-04

Related Terms

Sources

  1. Euler Finance V2 Whitepaper — docs.euler.finance (2024). Full technical specification of the Euler Vault Kit, EVC middleware, reactive IRM design, and sub-account system.
  1. Euler V1 Exploit Post-Mortem — Euler Finance Blog (March 2023). Detailed breakdown of the flash loan donation attack vector that enabled the $197M exploit, including the specific flawed self-liquidation logic.
  1. “Reactive Interest Rate Models for DeFi Lending” — Euler Research (2024). Technical paper describing the reactive IRM design, comparing it to Aave’s kinked model and Jump Rate Model variants.
  1. Euler V1 Hack Timeline: Negotiation and Recovery — Chainalysis Blog (April 2023). Timeline reconstruction of the weeks of on-chain negotiation between Euler and the exploiter, including the tx messages and final return of funds.
  1. “Permissionless Lending: Design Tradeoffs” — Gauntlet Network (2024). Risk analysis comparing permissionless vault models (Euler V2, Morpho Blue) against curated pool models (Aave, Compound) across efficiency, risk isolation, and manipulation resistance metrics.