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CVE-2023-34459
Good to know:
Date: June 16, 2023
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. 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.
Language: JS
Severity Score
Related Resources (5)
Severity Score
Weakness Type (CWE)
Improper Validation of Integrity Check Value
CWE-354Top Fix
Upgrade Version
Upgrade to version @openzeppelin/contracts - 4.9.2, @openzeppelin/contracts-upgradeable - 4.9.2
CVSS v3.1
Base Score: |
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Attack Vector (AV): | NETWORK |
Attack Complexity (AC): | LOW |
Privileges Required (PR): | NONE |
User Interaction (UI): | REQUIRED |
Scope (S): | CHANGED |
Confidentiality (C): | LOW |
Integrity (I): | LOW |
Availability (A): | NONE |