{"id":"CVE-2023-34459","summary":"OpenZeppelin Contracts's MerkleProof multiproofs may allow proving arbitrary leaves for specific trees","details":"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.\n\nA 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. This could happen deliberately if a malicious tree builder includes such a node in the tree.\n\nA 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.\n\nThe problem has been patched in version 4.9.2.\n\nSome 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.","aliases":["GHSA-wprv-93r4-jj2p"],"modified":"2026-08-12T03:51:39.958587225Z","published":"2023-06-16T22:13:18.181Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-354"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/34xxx/CVE-2023-34459.json"},"references":[{"type":"WEB","url":"https://github.com/OpenZeppelin/openzeppelin-contracts/releases/tag/v4.9.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/34xxx/CVE-2023-34459.json"},{"type":"ADVISORY","url":"https://github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-wprv-93r4-jj2p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-34459"},{"type":"FIX","url":"https://github.com/OpenZeppelin/openzeppelin-contracts/commit/4d2383e17186be3e8ccf5a442e9686ecc7de1c55"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/openzeppelin/openzeppelin-contracts","events":[{"introduced":"8c49ad74eae76ee389d038780d407cf90b4ae1de"},{"fixed":"e50c24f5839db17f46991478384bfda14acfb830"},{"fixed":"4d2383e17186be3e8ccf5a442e9686ecc7de1c55"}],"database_specific":{"source":["CPE_RANGE","REFERENCES"],"cpe":["cpe:2.3:a:openzeppelin:contracts:*:*:*:*:*:node.js:*:*","cpe:2.3:a:openzeppelin:contracts_upgradeable:*:*:*:*:*:node.js:*:*"],"extracted_events":[{"introduced":"4.7.0"},{"fixed":"4.9.2"}]}},{"type":"GIT","repo":"https://github.com/openzeppelin/openzeppelin-contracts-upgradeable","events":[{"introduced":"6b9807b0639e1dd75e07fa062e9432eb3f35dd8c"},{"fixed":"bc95521e34dcd49792065e264a7ad2b5a86f0091"}],"database_specific":{"cpe":"cpe:2.3:a:openzeppelin:contracts_upgradeable:*:*:*:*:*:node.js:*:*","extracted_events":[{"introduced":"4.7.0"},{"fixed":"4.9.2"}],"source":"CPE_RANGE"}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-34459.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N"}]}