vulnerability / NVI-00017562 / Revision 1
Zebra: Missing copy constraint in halo2_gadgets variable-base scalar multiplication allows under-constrained base, breaking Orchard Action circuit soundness
GitHub lists this reviewed advisory for zebrad, halo2_gadgets, orchard, zcash_primitives. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
9.3 critical
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
zebrad
source listed<= 4.5.1
### Summary A soundness vulnerability in the variable-base scalar multiplication gadget of `halo2_gadgets` allowed a malicious prover to produce a valid proof for an Orchard Action with an *under-constrained* base point. Because this gadget enforces the diversified-address-integrity condition of the Orchard Action statement, the flaw let a prover satisfy that condition for an arbitrary (pkd, gd, ivk) triple, effectively bypassing the check that binds an Action to the correct incoming viewing key — and therefore to the correct nullifier (nf) and spend validating key (ak) — of the note being spent. The main practical consequence is that an adversary could have performed a **double-spend within the Orchard pool**, resulting in a balance violation: the same note could be spent multiple times, each time revealing a distinct, valid-looking nullifier. The total ZEC supply was protected by Zcash's turnstile mechanism, which bounds value flowing out of any pool, so unbounded inflation of the overall supply was not possible; the exposure was inflation of value *within* the Orchard pool up to the turnstile-enforced limit. Exploiting the vulnerability via a double-spen
halo2_gadgets
source listed< 0.5.0
### Summary A soundness vulnerability in the variable-base scalar multiplication gadget of `halo2_gadgets` allowed a malicious prover to produce a valid proof for an Orchard Action with an *under-constrained* base point. Because this gadget enforces the diversified-address-integrity condition of the Orchard Action statement, the flaw let a prover satisfy that condition for an arbitrary (pkd, gd, ivk) triple, effectively bypassing the check that binds an Action to the correct incoming viewing key — and therefore to the correct nullifier (nf) and spend validating key (ak) — of the note being spent. The main practical consequence is that an adversary could have performed a **double-spend within the Orchard pool**, resulting in a balance violation: the same note could be spent multiple times, each time revealing a distinct, valid-looking nullifier. The total ZEC supply was protected by Zcash's turnstile mechanism, which bounds value flowing out of any pool, so unbounded inflation of the overall supply was not possible; the exposure was inflation of value *within* the Orchard pool up to the turnstile-enforced limit. Exploiting the vulnerability via a double-spen
orchard
source listed< 0.14.0
### Summary A soundness vulnerability in the variable-base scalar multiplication gadget of `halo2_gadgets` allowed a malicious prover to produce a valid proof for an Orchard Action with an *under-constrained* base point. Because this gadget enforces the diversified-address-integrity condition of the Orchard Action statement, the flaw let a prover satisfy that condition for an arbitrary (pkd, gd, ivk) triple, effectively bypassing the check that binds an Action to the correct incoming viewing key — and therefore to the correct nullifier (nf) and spend validating key (ak) — of the note being spent. The main practical consequence is that an adversary could have performed a **double-spend within the Orchard pool**, resulting in a balance violation: the same note could be spent multiple times, each time revealing a distinct, valid-looking nullifier. The total ZEC supply was protected by Zcash's turnstile mechanism, which bounds value flowing out of any pool, so unbounded inflation of the overall supply was not possible; the exposure was inflation of value *within* the Orchard pool up to the turnstile-enforced limit. Exploiting the vulnerability via a double-spen
zcash_primitives
source listed< 0.28.0
### Summary A soundness vulnerability in the variable-base scalar multiplication gadget of `halo2_gadgets` allowed a malicious prover to produce a valid proof for an Orchard Action with an *under-constrained* base point. Because this gadget enforces the diversified-address-integrity condition of the Orchard Action statement, the flaw let a prover satisfy that condition for an arbitrary (pkd, gd, ivk) triple, effectively bypassing the check that binds an Action to the correct incoming viewing key — and therefore to the correct nullifier (nf) and spend validating key (ak) — of the note being spent. The main practical consequence is that an adversary could have performed a **double-spend within the Orchard pool**, resulting in a balance violation: the same note could be spent multiple times, each time revealing a distinct, valid-looking nullifier. The total ZEC supply was protected by Zcash's turnstile mechanism, which bounds value flowing out of any pool, so unbounded inflation of the overall supply was not possible; the exposure was inflation of value *within* the Orchard pool up to the turnstile-enforced limit. Exploiting the vulnerability via a double-spen
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-ww9q-8r59-xv46 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.