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CVE-2023-34459: OpenZeppelin Contracts is a library for smart contract development

26
Routine
MEDIUM 5.3UPGRADEUPGRADE

CVE-2023-34459 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. Starting in version 4.7.0 and prior to version 4.9.2, when the `verifyMultiProof`, `verifyMultiProofCalldata`, `procesprocessMultiProof`, or `processMultiProofCalldat` functions are in use, it is possible to construct merkle trees that allow forging a valid multiproof for an arbitrary set of leaves. A contract may be vulnerable if it uses multiproofs for verification and the mer

Why this priority

  • No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score5.3 (Medium)
Attack vectorNetwork (remote)
Attack complexityHigh
Privileges neededLow
User interactionNone
EPSS exploit chance0.4% (top 69%)
CISA exploited listNo
WeaknessCWE-354
Published2023-06-16
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: >= 4.7.0 and < 4.9.2
Fixed in: 4.9.2
Safe to downgrade to: a release before 4.7.0
1. Check installed version
npm ls contracts
2. UPGRADE to 4.9.2
npm install contracts@">=4.9.2"
3. If no update is available yet, DOWNGRADE to a release before 4.7.0
npm view contracts versions npm install contracts@"<4.7.0"
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: >= 4.7.0 and < 4.9.2
Fixed in: 4.9.2
Safe to downgrade to: a release before 4.7.0
1. Check installed version
npm ls contracts-upgradeable
2. UPGRADE to 4.9.2
npm install contracts-upgradeable@">=4.9.2"
3. If no update is available yet, DOWNGRADE to a release before 4.7.0
npm view contracts-upgradeable versions npm install contracts-upgradeable@"<4.7.0"
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-2023-34459?

contracts: upgrade to 4.9.2; contracts upgradeable: upgrade to 4.9.2. Exact commands for each OS are on this page.

Is CVE-2023-34459 being exploited?

CVE-2023-34459 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-2023-34459 affect?

CVE-2023-34459 affects contracts, contracts upgradeable. Severity is medium (CVSS 5.3). OpenZeppelin Contracts is a library for smart contract development. Starting in version 4.7.0 and prior to version 4.9.2, when the `verifyMultiProof`, `verifyMultiProofCalldata`, `procesprocessMultiProof`, or `processMultiProofCalldat` func

How urgent is CVE-2023-34459?

Priority 26/100. No elevated risk signals yet.

Related CVEs

References

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