CVE-2026-54496
Zebra: Missing copy constraint in halo2_gadgets variable-base scalar multiplication allows under-constrained base, breaking Orchard Action circuit soundness
Impact
ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad 5.0.0, halo2_gadgets 0.5.0, orchard 0.14.0, zcash_primitives 0.28.0, and zcashd 6.20.0, the variable-base scalar multiplication gadget in halo2_gadgets/src/ecc/chip/mul/incomplete.rs used assign_advice() for the base point without a copy constraint tying it to the actual base, allowing a malicious prover to produce a valid proof for an Orchard Action with an under-constrained base point and bypass the diversified-address-integrity check that binds pk_d, g_d, ivk, the nullifier (nf), and the spend validating key (ak) to the note being spent. This issue is fixed in zebrad 5.0.0, halo2_gadgets 0.5.0, orchard 0.14.0, zcash_primitives 0.28.0, and zcashd 6.20.0.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | zebrad | <= 4.5.1 | 5.0.0 |
| rust | halo2_gadgets | < 0.5.0 | 0.5.0 |
| rust | orchard | < 0.14.0 | 0.14.0 |
| rust | zcash_primitives | < 0.28.0 | 0.28.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-ww9q-8r59-xv46
- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-ww9q-8r59-xv46
- https://github.com/ZcashFoundation/zebra/releases/tag/v5.0.0
- https://github.com/zcash/halo2/releases/tag/halo2_gadgets-0.5.0
- https://github.com/zcash/librustzcash/releases/tag/zcash_primitives-0.28.0
- https://github.com/zcash/orchard/releases/tag/0.14.0
- https://github.com/zcash/zcash/releases/tag/v6.20.0
- https://zfnd.org/zebra-4-5-3-and-5-0-0-emergency-soft-fork-and-nu6-2-activation