SNARK Verifier is a generic (S)NARK verifier

Why it is Yellow

• CVSS 6.9 medium

References

• https://github.com/axiom-crypto/snark-verifier/commit/d6aaf66d4706f5317cf61d5dbe00c14e7fbdbb70
• https://github.com/axiom-crypto/snark-verifier/releases/tag/v0.2.5
• https://github.com/axiom-crypto/snark-verifier/security/advisories/GHSA-265x-v3qf-ff6p

Original description

SNARK Verifier is a generic (S)NARK verifier. Prior to 0.2.5, KZG accumulator public-instance limbs are decoded without consistently enforcing canonical limb bounds before elliptic-curve coordinate reconstruction. `PlonkProof::read` selects scalars using `accumulator_indices` and passes them to `AccumulatorEncoding::from_repr`. For the EVM loader, `LimbsEncoding::from_repr` forwards them to `EvmLoader::ec_point_from_limbs` in `snark-verifier/src/loader/evm/loader.rs`, where `shl` and `add` reconstruct coordinates before `validate_ec_point` checks the resulting affine point rather than the original limb bounds. The related native path in `snark-verifier/src/pcs/kzg/accumulator.rs` can reach assertion- or unwrap-based decoding and panic instead of returning a verification error. This allows noncanonical encodings at the verifier boundary and can crash the native verifier. Standard SDK aggregation circuits are expected to constrain accumulator limbs before this boundary, which limits practical exploitability. This issue is fixed in version 0.2.5.