Vulnerability in Zcash Halo2 Gadgets
CVE-2026-54496
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:L.
EPSS exploit prediction
EPSS: 0.003 (23.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 23.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Zcash Halo2 Gadgets — versions < 0.5.0
- Zcash Librustzcash — versions < 0.28.0
- Zcash Orchard — versions < 0.14.0
- Zcash — versions < 6.20.0
- Zcashfoundation Zebra — versions < 5.0.0
Weakness classification (CWE)
References
- github.com/ZcashFoundation/zebra/releases/tag/v5.0.0
- github.com/ZcashFoundation/zebra/security/advisories/GHSA-ww9q-8r59-xv46
- github.com/zcash/halo2/releases/tag/halo2_gadgets-0.5.0
- github.com/zcash/librustzcash/releases/tag/zcash_primitives-0.28.0
- github.com/zcash/orchard/releases/tag/0.14.0
- github.com/zcash/zcash/releases/tag/v6.20.0
- zfnd.org/zebra-4-5-3-and-5-0-0-emergency-soft-fork-and-nu6-2-activation
Frequently asked questions
- What is CVE-2026-54496?
- CVE-2026-54496 is a critical-severity vulnerability in Zcash Halo2 Gadgets, classified under Insufficient Verification of Data Authenticity. CVSS score: 9.3/10. Published 2026-07-17.
- How severe is CVE-2026-54496?
- Critical severity. CVSS v3 base score is 9.3 out of 10.