CVE-2023-34234: Governor proposal creation may be blocked by frontrunning in OpenZeppelin

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-06-07 · updated 2026-06-17
Weakness: CWE-862

Description

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

How to fix

Upgrade to a fixed version: openzeppelin-contracts 4.9.1; OpenZeppelin Contracts Upgradeable 4.9.1. Check the vendor advisory for mitigations.

References

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