CVE-2023-34459
Description
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.
How to fix
- openzeppelin contracts4.9.2 or later
- openzeppelin contracts_upgradeable4.9.2 or later
- @openzeppelin/contracts4.9.2 or later
- @openzeppelin/contracts-upgradeable4.9.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| openzeppelin contracts | 4.7.0 ≤ v < 4.9.2 | 4.9.2 |
| openzeppelin contracts_upgradeable | 4.7.0 ≤ v < 4.9.2 | 4.9.2 |
| @openzeppelin/contractsnpm | 4.7.0 ≤ v < 4.9.2 | 4.9.2 |
| @openzeppelin/contracts-upgradeablenpm | 4.7.0 ≤ v < 4.9.2 | 4.9.2 |
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Attack Surface Management
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