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GHSA-7p92-x423-vwj6

Plonk verifier KZG multi point verification

Also known asGO-2023-2119
Published
Oct 17, 2023
Updated
Nov 8, 2023
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed

Blast Radius

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 versions0.9.1

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  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.

  4. How O3 protects you

    O3 pinpoints whether GHSA-7p92-x423-vwj6 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-7p92-x423-vwj6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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

Is GHSA-7p92-x423-vwj6 in your dependencies?

O3 detects GHSA-7p92-x423-vwj6 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.