Incident Overview
On September 3, 2024, the yield protocol Penpie was exploited for $27 million through a reentrancy vulnerability in its smart contracts.
The attacker exploited a reentrancy vulnerability by creating valueless versions of Pendle’s yield-bearing tokens (Standardized Yield, SY) and linking them to valuable assets. They deployed five malicious contracts mimicking legitimate liquidity pools, tricking Penpie’s rewards system. Using these fake SY tokens, they claimed real yield and executed three attack transactions between 6:25 PM and 6:42 PM UTC, siphoning $15.7 million in the first transaction and $5.6 million in the other two.
The attacker stole various assets including 695 rswETH, 4,101 agETH, 2,723 wstETH, and 2.52 million sUSDe. Pendle’s team managed to pause the contracts three minutes after the final attack, preventing further exploitation.
Exploiter:
https://etherscan.io/address/0x2f2dde66…f61c39
https://etherscan.io/address/0x69751b7e…cdeb52
https://etherscan.io/address/0x28e3fd9e…c74769
https://etherscan.io/address/0x7a2f4d62…a61d1b
Incident Report
Protocol Information
Market Context at Time of Hack
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.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Penpie, these are the critical security checks that could have prevented this incident (September 2024).
- 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.
Free TrialRelated Attack Classes
The technique used in this hack maps to these vulnerability classes in our security curriculum:
Proof-of-Concept Exploits
On-Chain Evidence & References
- Twitter/X Alert https://x.com/peckshield/status/1831072098669953388
- Twitter/X Alert https://x.com/AnciliaInc/status/1831080555292856476
- Twitter/X Alert https://x.com/hackenclub/status/1831383106554573099
- Twitter/X Alert https://x.com/Penpiexyz_io/status/1831462760787452240
Sources & References
- 01
- 02
- 03
Learn to Prevent the Next Penpie
The Penpie hack is one of many attacks that skilled auditors are trained to detect before deployment. Master real exploit patterns and defense techniques with hands-on Web3 security training.