CVE-2023-34459
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OpenZeppelin Contracts's MerkleProof multiproofs may allow proving arbitrary leaves for specific trees
rank 19 = 0 + 15 + 0 + 4 + 0
rank@v1 · backlog
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.00371 · without this subject the record ranks 19
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 5.9, from NVD · without this subject the record ranks 4
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 19
How much of the world it touches
NVD CPE configurations
2 products in the CPE ranges · without this subject the record ranks 15
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 19
$11,300 = $4.99M incident cost x 0.6121449559255632 exposure x 0.00371 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
No weakness class or product neighbourhood is held for this record, so this index cannot name anywhere to check next. That is an absence in the record, not a finding about the software.
Sources disagree here.
Both shown, dated. We don't pick winners. disagreement-rules@v1
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Harm, if it fires from the vector and the weakness
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Nothing observed in held sources.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
Attack path
What it is stated by the CNA
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 merkle tree that is processed includes a node with value 0 at depth 1 (just under the root). This could happen inadvertedly for balanced trees with 3 leaves or less, if the leaves are not hashed. receipt
Read the rest of the CNA's description
This could happen deliberately if a malicious tree builder includes such a node in the tree. A contract is not vulnerable if it uses single-leaf proving (`verify`, `verifyCalldata`, `processProof`, or `processProofCalldata`), or if it uses multiproofs with a known tree that has hashed leaves. Standard merkle trees produced or validated with the @openzeppelin/merkle-tree library are safe. The problem has been patched in version 4.9.2. Some workarounds are available. For those using multiproofs: When constructing merkle trees hash the leaves and do not insert empty nodes in your trees. Using the @openzeppelin/merkle-tree package eliminates this issue. Do not accept user-provided merkle roots without reconstructing at least the first level of the tree. Verify the merkle tree structure by reconstructing it from the leaves.
NVD's analysis a second authority
- severity
- 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- weakness
- CWE-354
- affected versions
- openzeppelin contracts >= 4.7.0 < 4.9.2; openzeppelin contracts upgradeable >= 4.7.0 < 4.9.2
- also scored by
- [email protected] 5.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
The CNA scored it 5.3 and NVD 5.9. Both are shown because both were published; we do not pick one.
check it yourself github.com github.com github.com receipt
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 23 observations
23 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The full biography
Exploit probability more than doubled between 2025-11-18 and 2025-11-21 (0.00111 → 0.00632) and the record had been public for 3 years when this index was last written.
Siblings and hubs
Records related to this one
No record cites this identifier and it carries no alias. Its defect family is below.
Its defect family
openzeppelin-contracts
Of the 2 records in this family, this is the only one whose title names merkleproof multiproofs proving.
Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.
Family membership: held values
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What usually comes next
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