# CVE-2026-104422: Zebra before 6.3.0 Block Sync Denial of Service via Coinbase scriptSig Rewrite

> A malicious peer can delay Zebra node synchronization by serving blocks with manipulated coinbase scriptSigs, causing a denial of service.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Oct 2026
- **Updated:** 2 Oct 2026
- **Also known as:** GHSA-3qff-7hrr-r4g7, GHSA-g95h-hw6g-pvgv

## What is CVE-2026-104422?

CVE-2026-104422 is a high-severity denial of service vulnerability in ZcashFoundation zebra, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The block sync download path in Zebra (zebrad) before 6.3.0 reads a block's height from its unvalidated coinbase scriptSig and drops blocks that appear too far behind the tip before consensus validation, without penalizing the supplying peer. Because V5 transaction IDs exclude the scriptSig, a malicious peer can repeatedly serve a canonical block whose coinbase claims height 1 while keeping the requested hash, delaying the node's discovery of the newest block.

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

## Which versions are affected by CVE-2026-104422?


## How do I fix CVE-2026-104422?

No fix has been published for CVE-2026-104422 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104422 being exploited?

There is no known exploitation of CVE-2026-104422 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104422 and fix it if it is affected.

What it is: CVE-2026-104422 is a high-severity denial of service vulnerability in ZcashFoundation zebra, published on 2 Oct 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-2026-104422 in the wild and no public exploit code.

Affected product: ZcashFoundation zebra. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-104422/ (Markdown: https://insights.sbomify.com/CVE-2026-104422/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104422
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104422
- OSV: https://osv.dev/vulnerability/CVE-2026-104422

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-104422/
Summaries are generated and may contain mistakes; the official description above is the record.