# CVE-2026-123556: Zebra 4.5.0 before 7.0.0 Honest Peer Ban via Mempool Lock-Time Scoring


- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 8 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-5h3r-fpmj-483w, GHSA-7gc8-jc34-45g3

## What is CVE-2026-123556?

CVE-2026-123556 is a medium-severity vulnerability in ZcashFoundation zebra, published on 8 Nov 2026. 

### Official description

ZcashFoundation Zebra from 4.5.0 before 7.0.0 contains a protection mechanism failure that bans honest peers by scoring mempool lock-time rejections at the ban threshold. Attackers can broadcast transactions locked until the current height right after each block, causing lagging nodes to ban honest relaying peers for 24 hours or until restart.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-123556?


## How do I fix CVE-2026-123556?

No fix has been published for CVE-2026-123556 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-123556 being exploited?

There is no known exploitation of CVE-2026-123556 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123556 and fix it if it is affected.

What it is: CVE-2026-123556 is a medium-severity vulnerability in ZcashFoundation zebra, published on 8 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-123556 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-2026-123556/ (Markdown: https://insights.sbomify.com/CVE-2026-123556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123556
- OSV: https://osv.dev/vulnerability/CVE-2026-123556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123556/
Summaries are generated and may contain mistakes; the official description above is the record.