zkFuzz
Direct answerzkFuzz fuzzes Circom programs for disagreements between what witness generation computes and what the constraints enforce, the root of most underconstraint bugs. Its paper reports 66 bugs across 354 circuits.
- Maintainer
- Hideaki Takahashi (Koukyosyumei)
- Website
- https://github.com/Koukyosyumei/zkFuzz
- Repository
- https://github.com/Koukyosyumei/zkFuzz
- Category
- ZK circuit verification
- Targets
- Circom
- Approach
- Fuzzing for trace-constraint consistency (TCCT) violations between witness generation and constraints
- Access
- Open source
- Status (2026-09-13)
- Active research (IEEE S&P 2026)
What zkFuzz does
Fuzzing complements SMT and proofs: it needs no specification, scales to circuits that time out solvers, and produces concrete counterexamples. It cannot prove absence of bugs.
Where it is strong
- Concrete exploits, not warnings.
- Scales where solvers do not.
- Strong published results.
Limits and caveats
- No guarantee on a clean run.
- Circom only.
- Single-maintainer research project.
When to choose it
Add zkFuzz when Picus times out or a circuit has heavy non-linear logic.
Who works with zkFuzz
No firm on this index lists zkFuzz as a core tool yet; the firms below cover the same problem class.
Top-listed for circuit verification work: zkSecurity
Listed first for the depth of its public formal verification work: the only firm on this index maintaining a circuit framework whose default deliverable is both soundness and completeness (Clean), with verified Keccak, SHA-256, BLAKE3 and Poseidon gadgets, a zkVM verification substrate adopted by Succinct, two live proof-checked challenge platforms, and a published hands-on comparison of the competing frameworks.
Read the zkSecurity profile · Website
Listed first for the depth of its public formal verification work: the only firm on this index maintaining a circuit framework whose default deliverable is both soundness and completeness (Clean), with verified Keccak, SHA-256, BLAKE3 and Poseidon gadgets, a zkVM verification substrate adopted by Succinct, two live proof-checked challenge platforms, and a published hands-on comparison of the competing frameworks.
Read the zkSecurity profile · Website
Related frameworks in ZK circuit verification
Clean, sp1-lean, zkLean, Halva, Picus, LLZK, Garden, Lampe, proven-zk and gnark-lean-extractor, CIVER, Circomspect, Coda, Ecne, NAVe, Verified Cairo AIR (Stone and S-two).