Siren Hack

TOTAL LOST $3.5M
Medium Reentrancy polygon

Summarize with AI

Affected Chain polygon Incident surface
Recovered - No recovery reported
All-Time Rank #515 By amount stolen
Auditors 1 Prior security audit

Incident Overview

Decentralized option markets on Ethereum.

Incident Report

Protocol / Project Siren
Date of Incident
Affected Chain(s) polygon
Attack Technique Reentrancy
Classification Smart Contract Language
Primary Source View Post-Mortem

Protocol Information

Protocol Type Options
Smart Contract Language Solidity
Official Website siren.xyz/
Protocol Twitter/X @sirenprotocol

Market Context at Time of Hack

Token Categories
AI & Big Data Memes BNB Chain Ecosystem AI Agents Binance Alpha Four.Meme Ecosystem Binance Ecosystem Binance Listing

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 reentrancy and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with polygon smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in Siren's contract logic - root cause: smart contract language
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 Reentrancy vulnerabilities in code review
Audited by Audit Report 1 — still lost $3.5M. Prior audits don't guarantee safety, especially after post-audit code changes.

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

  • Verify all logic paths related to Reentrancy are guarded by proper access controls and input validation - see the Reentrancy 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

Related Attack Classes

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

See all Reentrancy examples →

Sources & References

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