Immunefi informed our team of a critical vulnerability in the TimelockController contract in OpenZeppelin Contracts, our open source smart contracts library. In this document, we will share an overview of the affected smart contract, the technical details of the vulnerability, and our assessment of the issue. We will also provide transparency regarding the development process for all OpenZeppelin Contracts, lessons learned, and next steps to further harden the security of the library.
Of the projects potentially exposed, we determined — to the best of our ability — that no critical instance of the vulnerability contained assets at risk. OpenZeppelin released a bug fix analysis. Whitehat Zb3 submitted a serious reentrant vulnerability in OpenZeppelin's TimelockController contract on August 21, 2021, which affected a project hosted on the Immunefi vulnerability bounty platform. The project chose to remain anonymous and has paid an undisclosed amount (including an anonymous bonus) to White Hat. OpenZeppelin paid White Hat a bonus of $25,000 to recognize their contribution to community security and released a patch. As far as it knows, this is the only serious vulnerability that OpenZeppelin has in its open source smart contract library. The vulnerability has been patched in the affected projects, and OpenZeppelin has released an updated contract version to fix the vulnerability. All projects that use TimelockController should be migrated.
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