The Informal Security Review of the Patch to Fix the Vulnerability of the Poly Network Hack

This blog presents an informal security review of the patch implemented to fix the recent vulnerability in Poly network, highlighting the use of allow lists and the resulting security properties.

The Informal Security Review of the Patch to Fix the Vulnerability of the Poly Network Hack

In this blog, we will share our informal security review of the patch to fix the recent Poly network vulnerability.


We only provide an informal security review of the patch. Our evaluation shows that the patch can fix the vulnerability that was previously attacked on Aug 10, 2021. However, our review does not guarantee that there do not exist other vulnerabilities in other components of the project.

Our review

Basically, the method to fix the vulnerability is using allow lists. The allow lists are initialized when creating the EthCrossChainManager. By doing so, this patch can ensure the following security properties.

  • Property one: Only the contract in the allow lists can invoke the crossChain function, which is used to start the cross-chain transaction.
  • Property two: Only the method and the contract in the allow lists can be invoked by the cross-chain transaction.

By enforcing the above properties, we think the patch can fix the vulnerability.

Note that, we only review the specific patch that is used to fix the vulnerability for BSC and Ethereum. We are not sure whether other chains with the native support of cross-chain transactions have the security property one or not (without reviewing the change of the corresponding code). Besides, this patch does not perform the security enhancement on the Poly chain, which we think, could be a better place for security policies (without trusting the source and destination chain.)

Credits: Yufeng Hu, Siwei Wu, Lei Wu, Yajin Zhou @ BlockSecTeam

About BlockSec

BlockSec is a pioneering blockchain security company established in 2021 by a group of globally distinguished security experts. The company is committed to enhancing security and usability for the emerging Web3 world in order to facilitate its mass adoption. To this end, BlockSec provides smart contract and EVM chain security auditing services, the Phalcon platform for security development and blocking threats proactively, the MetaSleuth platform for fund tracking and investigation, and MetaSuites extension for web3 builders surfing efficiently in the crypto world.

To date, the company has served over 300 esteemed clients such as MetaMask, Uniswap Foundation, Compound, Forta, and PancakeSwap, and received tens of millions of US dollars in two rounds of financing from preeminent investors, including Matrix Partners, Vitalbridge Capital, and Fenbushi Capital.

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