---
id: "CVE-2026-123554"
page: "https://infrastack.ai/live/CVE-2026-123554"
kind: "vulnerability"
aliases: ["CVE-2026-123554"]
title: "Zebra: mempool coinbase check lets peers pin CPU threads"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["runtime", "self-hosted", "zcash", "zebra", "zebrad"]
not_affected_if: ["outbound-only-peers", "version-7-or-later"]
published_at: "2026-11-08T02:16:47+00:00"
first_seen_at: "2026-11-08T02:21:11+00:00"
updated_at: "2026-11-08T02:23:10+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123554", "first_seen_at": "2026-11-08T02:21:11+00:00"}]
exploit_sources: []
---

# Zebra: mempool coinbase check lets peers pin CPU threads

Link for people: https://infrastack.ai/live/CVE-2026-123554 (this .md is for agents)

Zebra zebrad 6.4.0 before 7.0.0 rebuilds a transaction's output list once per spent input during the mempool coinbase-maturity check, so the work grows quadratically. Any connected peer can send unsigned transactions with many inputs and outputs, which are rejected without penalty, to keep verification threads busy.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the running zebrad version with `zebrad --version` and see whether it falls in 6.4.0 up to but not including `7.0.0`.
- Confirm the node accepts peer connections from the internet (default P2P port exposed).

## Fix

- Zebra `7.0.0` (fixed version per the product range).

## Timeline

- 2026-11-08T02:21:11+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123554

## Documents

- [advisory] Vendor advisory: github.com https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-7jp4-mq53-4cvq
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/zebra-zebrad-6.4.0-before-7.0.0-denial-of-service-via-mempool-coinbase-maturity-check
- [fix] Patch: github.com https://github.com/ZcashFoundation/zebra/commit/08743d669b33a19bce2a5d54001bd468c03a196e

## From the sources

Zebra zebrad 6.4.0 before 7.0.0 performs quadratic work in the mempool coinbase-maturity check because Transaction::coinbase_spend_restriction() rebuilds the transaction's output list once per spent outpoint. Any connected peer can repeatedly send unsigned transactions with many transparent inputs and outputs, which are rejected without a misbehavior score, to pin verification threads.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_