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CVE-2023-34234: OpenZeppelin Contracts is a library for smart contract development

36
Routine
MEDIUM 5.3REMOTEUPGRADEUPGRADE

CVE-2023-34234 is a medium-severity flaw (CVSS 5.3) affecting contracts, contracts upgradeable. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score5.3 (Medium)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance0.6% (top 52%)
CISA exploited listNo
WeaknessCWE-862
Published2023-06-07
Last modified2026-06-17
Publisher (CNA): GitHub, Inc. · Vendor: openzeppelin

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

openzeppelin contracts UPGRADE
Affected: >= 4.3.0 and < 4.9.1
Fixed in: 4.9.1
Safe to downgrade to: a release before 4.3.0
1. Check installed version
npm ls contracts
2. UPGRADE to 4.9.1
npm install contracts@">=4.9.1"
3. If no update is available yet, DOWNGRADE to a release before 4.3.0
npm view contracts versions npm install contracts@"<4.3.0"
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
openzeppelin contracts upgradeable UPGRADE
Affected: >= 4.3.0 and < 4.9.1
Fixed in: 4.9.1
Safe to downgrade to: a release before 4.3.0
1. Check installed version
npm ls contracts-upgradeable
2. UPGRADE to 4.9.1
npm install contracts-upgradeable@">=4.9.1"
3. If no update is available yet, DOWNGRADE to a release before 4.3.0
npm view contracts-upgradeable versions npm install contracts-upgradeable@"<4.3.0"
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-34234?

contracts: upgrade to 4.9.1; contracts upgradeable: upgrade to 4.9.1. Exact commands for each OS are on this page.

Is CVE-2023-34234 being exploited?

CVE-2023-34234 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-34234 affect?

CVE-2023-34234 affects contracts, contracts upgradeable. Severity is medium (CVSS 5.3). 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

How urgent is CVE-2023-34234?

Priority 36/100. Remotely exploitable, no login, no user action

Related CVEs

References

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