# CVE-2026-54496: Zebra: Missing copy constraint in halo2_gadgets variable-base scalar multiplication allows under-constrained base, breaking Orchard Action circuit soundness

> A missing copy constraint in Zcash's halo2_gadgets allows malicious provers to bypass diversified-address-integrity checks in Orchard Action circuits.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-ww9q-8r59-xv46

## What is CVE-2026-54496?

CVE-2026-54496 is a critical vulnerability in ZcashFoundation halo2_gadgets, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-54496?

8 open source packages ship an affected version, including halo2_gadgets, orchard and zcash_primitives.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `halo2_gadgets` | crates.io | All versions | 0.5.0 |
| `halo2_gadgets` | crates.io | All versions | 0.5.0 |
| `orchard` | crates.io | All versions | 0.14.0 |
| `orchard` | crates.io | All versions | 0.14.0 |
| `zcash_primitives` | crates.io | All versions | 0.28.0 |
| `zcash_primitives` | crates.io | All versions | 0.28.0 |
| `zebrad` | crates.io | All versions | 5.0.0 |
| `zebrad` | crates.io | All versions | 5.0.0 |

## How do I fix CVE-2026-54496?

Upgrade halo2_gadgets to 0.5.0 or later.

## Is CVE-2026-54496 being exploited?

There is no known exploitation of CVE-2026-54496 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54496 and fix it if it is affected.

What it is: CVE-2026-54496 is a critical vulnerability in ZcashFoundation halo2_gadgets, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54496 in the wild and no public exploit code.

Affected packages and fixed versions:
- halo2_gadgets (crates.io): affected all versions; fixed in 0.5.0
- halo2_gadgets (crates.io): affected all versions; fixed in 0.5.0
- orchard (crates.io): affected all versions; fixed in 0.14.0
- orchard (crates.io): affected all versions; fixed in 0.14.0
- zcash_primitives (crates.io): affected all versions; fixed in 0.28.0
- zcash_primitives (crates.io): affected all versions; fixed in 0.28.0
- zebrad (crates.io): affected all versions; fixed in 5.0.0
- zebrad (crates.io): affected all versions; fixed in 5.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54496/ (Markdown: https://insights.sbomify.com/CVE-2026-54496/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54496
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54496
- OSV: https://osv.dev/vulnerability/CVE-2026-54496

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54496/
Summaries are generated and may contain mistakes; the official description above is the record.