PunkProtocol

title	Punk Protocol Re-initialize
description	Taking control by re-initializing proxy contracts
type	Exploit
network	ethereum
date	2021-08-10
loss_usd	8950000
returned_usd	4950000
tags	access control reinitialization
subcategory
vulnerable_contracts	0x3BC6aA2D25313ad794b2D67f83f21D341cc3f5fb 0x1F3b04c8c96A31C7920372FFa95371C80A4bfb0D 0x929cb86046E421abF7e1e02dE7836742654D49d6
tokens_lost	Punk USDT Punk USDC Punk DAI
attacker_addresses	0x1D5a56402425C1099497C1AD715A6b56aACcB72B
malicious_token
attack_block	12995895
reproduction_command	forge test --match-contract Exploit_Punk -vvv
attack_txs	0x7604c7dd6e9bcdba8bac277f1f8e7c1e4c6bb57afd4ddf6a16f629e8495a0281
sources	title url Rekt News Report https://rekt.news/punkprotocol-rekt title url Postmortem https://medium.com/punkprotocol/punk-finance-fair-launch-incident-report-984d9e340eb

Step-by-step

1. Call initialize to set your own forge_ address
2. Call withdrawToForge to withdraw tokens

Detailed Description

The Punk protocol pools did not prevent someone from calling initialize after the contracts were already initialized.

The attacker called initialize through the proxy and set their own forge_ address, which allowed them to later call withdrawToForge, which, as the name implies, withdraws all the funds to the forge address.

    function initialize(
        address forge_,
        address token_,
        address cToken_,
        address comp_,
        address comptroller_,
        address uRouterV2_ ) public {
    }

Possible mitigations

• initialize functions should always be protected so they can be called only once