CVE-2023-34459Public exploitNetwork attack vector

Arbitrary leaf proofs via unconsumed multiproof elements

Published Jun 16, 2023 · Updated Dec 16, 2024

Improper multiproof validation in OpenZeppelin Contracts 4.7.0 through 4.9.1 allows attackers to prove arbitrary Merkle leaves. The MerkleProof multiproof processors return the final computed hash without confirming that every supplied proof element was consumed. Reachability requires multiproof verification against a tree with a zero-valued node directly below its root; single proofs and hashed-leaf standard trees are unaffected.

CVSS severity5.9
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper multiproof validation in OpenZeppelin Contracts 4.7.0 through 4.9.1 allows attackers to prove arbitrary Merkle leaves. The MerkleProof multiproof processors return the final computed hash without confirming that every supplied proof element was consumed. Reachability requires multiproof verification against a tree with a zero-valued node directly below its root; single proofs and hashed-leaf standard trees are unaffected.

The record

CVE
CVE-2023-34459
Published
Jun 16, 2023
Updated
Dec 16, 2024
Vendor
OpenZeppelin
Product
OpenZeppelin Contracts
Classifications
CWE-354
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 16, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.7.0, < 4.9.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenZeppelin · OpenZeppelin Contractsversion=>= 4.7.0, < 4.9.2

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-354Improper Validation of Integrity Check Value

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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