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Plonk verifier KZG multi point verificationGHSA-7p92-x423-vwj6

Fix: Consensys/gnark@3421eaa

GHSA-7p92-x423-vwj6 is a security vulnerability in github.com/consensys/gnark. A fix is available for github.com/consensys/gnark — see the affected versions and patch details below.

Also known asGO-2023-2119
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 8, 2023 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected
🐹github.com/consensys/gnark

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The vulnerability allows a third party to derive a valid proof from a valid initial tuple {proof, public_inputs}, corresponding to the same public inputs as the initial proof. It is due to a randomness being generated using a small part of the scratch memory describing the state, allowing for degrees of freedom in the transcript.

Note that the impact is limited to the PlonK verifier smart contract.

Patches

We still use a hash function on some data to have a pseudo rng, but instead of hashing the first 32 bytes of the state ( let random := mod(keccak256(state, 0x20), r_mod) )

we hash the whole state at this point of the verifier as if it was a Fiat Shamir transcript:

        mstore(mPtr, mload(add(state, STATE_FOLDED_DIGESTS_X)))
        mstore(add(mPtr, 0x20), mload(add(state, STATE_FOLDED_DIGESTS_Y)))
        mstore(add(mPtr, 0x40), calldataload(add(aproof, PROOF_BATCH_OPENING_AT_ZETA_X)))
        mstore(add(mPtr, 0x60), calldataload(add(aproof, PROOF_BATCH_OPENING_AT_ZETA_Y)))
        mstore(add(mPtr, 0x80), calldataload(add(aproof, PROOF_GRAND_PRODUCT_COMMITMENT_X)))
        mstore(add(mPtr, 0xa0), calldataload(add(aproof, PROOF_GRAND_PRODUCT_COMMITMENT_Y)))
        mstore(add(mPtr, 0xc0), calldataload(add(aproof, PROOF_OPENING_AT_ZETA_OMEGA_X)))
        mstore(add(mPtr, 0xe0), calldataload(add(aproof, PROOF_OPENING_AT_ZETA_OMEGA_Y)))
        mstore(add(mPtr, 0x100), mload(add(state, STATE_ZETA)))
        mstore(add(mPtr, 0x120), mload(add(state, STATE_GAMMA_KZG)))
        let random := staticcall(gas(), 0x2, mPtr, 0x140, mPtr, 0x20)

Workarounds

In the function batch_verify_multi_points, the variable random (corresponding to u in the paper, step 12 of the plonk verification process) should depend on state_folded_digests_x, state_folded_digests_y, proof_grand_product_commitment_x, proof_grand_product_commitment_y and state_zeta (by hashing those values for instance).

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/consensys/gnarkall versions0.9.1go get github.com/consensys/gnark@v0.9.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/consensys/gnark, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/consensys/gnark to 0.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7p92-x423-vwj6 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact The vulnerability allows a third party to derive a valid proof from a valid initial tuple {proof, public_inputs}, corresponding to the same public inputs as the initial proof. It is due to a randomness being generated using a small part of the scratch memory describing the state, allowing for degrees of freedom in the transcript. Note that the impact is limited to the PlonK verifier smart contract. ### Patches We still use a hash function on some data to have a pseudo rng, but instead of hashing the first 32 bytes of the state ( ` let random := mod(keccak256(state, 0x20), r_mod)
O3 Security · Impact-Aware SCA

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Plonk verifier KZG multi point verification