CVE-2023-34234: Openzeppelin Contracts

Medium severity, CVSS 5.3. EPSS: 0.6% chance of exploitation in the next 30 days.

OpenZeppelin Contracts is a library for smart contract development. By frontrunning the creation of a proposal, an attacker can become the proposer and gain the ability to cancel it. The attacker can do this repeatedly to try to prevent a proposal from being proposed at all. This impacts the `Governor` contract in v4.9.0 only, and the `GovernorCompatibilityBravo` contract since v4.3.0. This problem has been patched in 4.9.1 by introducing opt-in frontrunning protection. Users are advised to upgrade. Users unable to upgrade may submit the proposal creation transaction to an endpoint with frontrunning protection as a workaround.

Affected products

• Openzeppelin Contracts: from 4.3.0, before 4.9.1 (fixed in 4.9.1)
• Openzeppelin Contracts Upgradeable: from 4.3.0, before 4.9.1 (fixed in 4.9.1)

Published 2023-06-07. Last modified 2026-06-17.