How severe is CVE-2023-34234?

CVE-2023-34234 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-34234?

CVE-2023-34234 affects the following packages: @openzeppelin/contracts (npm), @openzeppelin/contracts-upgradeable (npm). Ecosystems affected: npm.

How do I fix CVE-2023-34234?

Update @openzeppelin/contracts to 4.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34234 is resolved across your whole dependency graph.

How do I detect CVE-2023-34234 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @openzeppelin/contracts. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2023-34234 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2023-34234?

O3 pinpoints whether CVE-2023-34234 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2023-34234 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-34234 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-34234?

CVE-2023-34234 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 44th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2023-34234 published, and has it been updated?

CVE-2023-34234 was published on June 7, 2023 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

CVE-2023-34234

MEDIUM

Governor proposal creation may be blocked by frontrunning in OpenZeppelin

Also known asGHSA-5h3x-9wvq-w4m2

Published

Jun 7, 2023

Updated

Apr 10, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk44th percentile+0.49%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

2 pkgs affected

📦@openzeppelin/contracts📦@openzeppelin/contracts-upgradeable

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

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 Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@openzeppelin/contracts`	≥ 4.3.0&&< 4.9.1	4.9.1
📦npm	`@openzeppelin/contracts-upgradeable`	≥ 4.3.0&&< 4.9.1	4.9.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @openzeppelin/contracts. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @openzeppelin/contracts to 4.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34234 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2023-34234 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2023-34234. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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 front

O3 Security · Impact-Aware SCA

Is CVE-2023-34234 in your dependencies?

O3 detects CVE-2023-34234 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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