CVE-2023-34459

Summary

CVE-2023-34459 is a vulnerability affecting OpenZeppelin Contracts, a popular library for smart contract development. This issue, present in versions 4.7.0 to 4.9.1, allows for the construction of manipulated merkle trees that can forge a valid multiproof for any desired set of leaves. Contracts that utilize multiproofs for verification and process unhashed leaves or include nodes with a depth of 1 and a value of 0 are at risk. Version 4.9.2 of OpenZeppelin Contracts has addressed this vulnerability. To mitigate the risk, developers should hash leaves before constructing merkle trees, avoid empty nodes, and verify the merkle tree structure instead of accepting user-provided roots. Using the @openzeppelin/merkle-tree library is another effective solution.

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