# CVE-2026-52739: ZEBRA: Repeated Non-Finalized Shielded Transaction Aborts Zebra Before Duplicate-Nullifier Rejection

> A malicious block producer can crash the Zebra Zcash node by including duplicate shielded transactions in consecutive blocks, causing a process abort.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-hhm7-qrv5-h4r6

## What is CVE-2026-52739?

CVE-2026-52739 is a medium-severity denial of service vulnerability in ZcashFoundation zebra, published on 18 Aug 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 4.5.0, a malicious block producer can terminate zebrad by placing the same shielded transaction in a non-finalized parent block and its child. In zebra-state/src/service/non_finalized_state/chain.rs, Chain::push originally inserted the transaction hash into tx_loc_by_hash and asserted uniqueness before updating shielded data and running the duplicate Sprout, Sapling, or Orchard nullifier checks. The repeated transaction therefore reached the transactions must be unique within a single chain assertion before contextual validation could reject it cleanly. Zebra release builds use panic equals abort, so the reachable assertion terminates the entire process; exploitation requires either two consecutive attacker-mined blocks or an attacker-mined child immediately after an honest block includes the attacker's shielded transaction. This issue is fixed in version 4.5.0.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-52739?

4 open source packages ship an affected version, including zebra-state and zebrad.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zebra-state` | crates.io | All versions | 7.0.0 |
| `zebra-state` | crates.io | All versions | 7.0.0 |
| `zebrad` | crates.io | All versions | 4.5.0 |
| `zebrad` | crates.io | All versions | 4.5.0 |

## How do I fix CVE-2026-52739?

Upgrade zebra-state to 7.0.0 or later.

## Is CVE-2026-52739 being exploited?

There is no known exploitation of CVE-2026-52739 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52739 and fix it if it is affected.

What it is: CVE-2026-52739 is a medium-severity denial of service vulnerability in ZcashFoundation zebra, published on 18 Aug 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-2026-52739 in the wild and no public exploit code.

Affected packages and fixed versions:
- zebra-state (crates.io): affected all versions; fixed in 7.0.0
- zebra-state (crates.io): affected all versions; fixed in 7.0.0
- zebrad (crates.io): affected all versions; fixed in 4.5.0
- zebrad (crates.io): affected all versions; fixed in 4.5.0

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-2026-52739/ (Markdown: https://insights.sbomify.com/CVE-2026-52739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52739
- OSV: https://osv.dev/vulnerability/CVE-2026-52739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52739/
Summaries are generated and may contain mistakes; the official description above is the record.