apegurus/parity-multisig

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Parity Multisig Freeze (2017)

Overview

In November 2017, a user accidentally triggered a vulnerability in the Parity Multisig wallet library contract. By calling an uninitialized initWallet function, the user became the owner of the library contract and subsequently called kill(), which executed selfdestruct. This froze approximately 513,000 ETH (worth ~$150M at the time) across 587 wallets that depended on this library.

Root Cause

The Parity Multisig wallets used delegatecall to execute logic from a shared library contract. However, the library contract itself was not initialized. This allowed any user to call the initWallet function on the library contract directly, making them the owner of the library. Once they were the owner, they could call the kill function, which contained a selfdestruct instruction.

Attack Flow

1. A user (devops199) found the uninitialized library contract.
2. The user called initWallet() on the library contract, becoming its owner.
3. The user then called kill() on the library contract.
4. The library contract executed selfdestruct, removing its code from the blockchain.
5. All multisig wallets that used delegatecall to this library now had no logic to execute, effectively freezing all funds held in them.

Impact

• Loss: ~$150M (513k ETH)
• Protocol: Parity Multisig
• Chain: Ethereum
• Date: 2017-11-06

Key Transactions

• Initialization tx: 0x05f5c113c130f928d4d0d261046c5511846909b77060ef6568bf9158ad312a06
• Kill tx: 0x47f7cff3ad8733831a0e273108ef239bb0d0657da3a4279b1d17ac2616a12487

Detection Heuristics

• Pattern 1: Uninitialized library contracts that contain sensitive functions like selfdestruct or init.
• Pattern 2: Use of delegatecall to a contract that can be destroyed or modified by unauthorized users.

Remediation

• Fix 1: Initialize library contracts during deployment or use a constructor to disable initialization functions.
• Fix 2: Avoid using selfdestruct in library contracts.
• Fix 3: Use static libraries or ensure the target of delegatecall is immutable and properly initialized.

References

• rekt.news/parity-rekt/
• paritytech.io/blog/security-alert-heavy-update/