---
id: CVE-2026-104431
title: >-
  Zebra before 6.0.0 contains a denial of service vulnerability that allows
  unauthenticated peers to stall Tokio workers by submitting mempool
  transactions requiring expensive synchronous script verification
summary: >-
  Zebra before 6.0.0 contains a denial of service vulnerability that allows
  unauthenticated peers to stall Tokio workers by submitting mempool
  transactions requiring expensive synchronous script verification. Attackers
  can send non-standar…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-405
vendor: ZcashFoundation
product: zebra
affected:
  - zebra < 6.0.0
published: '2026-10-02'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T12:17:13.610'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-104431'
references:
  - url: >-
      https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-84j3-rw4c-gqmj
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/zebra-before-6.0.0-denial-of-service-via-synchronous-script-ffi-verification
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-02T12:17:44.333Z'
---

## Overview

Zebra before 6.0.0 contains a denial of service vulnerability that allows unauthenticated peers to stall Tokio workers by submitting mempool transactions requiring expensive synchronous script verification. Attackers can send non-standard high-sigop P2SH transactions that reach CachedFfiTransaction::is_valid() before standardness checks, saturating the verifier buffer and rendering the node unresponsive.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.