CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
Percentile
38.5%
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.
Vendor | Product | Version | CPE |
---|---|---|---|
openzeppelin | contracts | * | cpe:2.3:a:openzeppelin:contracts:*:*:*:*:*:node.js:*:* |
openzeppelin | contracts_upgradeable | * | cpe:2.3:a:openzeppelin:contracts_upgradeable:*:*:*:*:*:node.js:*:* |
[
{
"vendor": "OpenZeppelin",
"product": "openzeppelin-contracts",
"versions": [
{
"version": ">= 4.7.0, < 4.9.2",
"status": "affected"
}
]
}
]