Zebra: Consensus divergence via V5 SIGHASH_SINGLE without output

Summary

Zebra 4.4.0 (zebrad) and zebra-script 6.0.0 fail to enforce a ZIP-244 consensus rule for V5 transparent transactions. Inputs signed with SIGHASH_SINGLE that have no matching output are accepted. An attacker can broadcast crafted transactions or blocks that Zebra accepts but zcashd rejects, splitting Zebra nodes from the rest of the Zcash network. The attack requires no authentication and no user interaction.

Affected

• zebrad (Zebra node) 4.4.0 to before 4.4.1
• zebra-script 6.0.0 to before 6.0.1

Fixed in

• zebrad 4.4.1
• zebra-script 6.0.1

Workaround

Unknown. The vendor documents no workaround; upgrading is the only remedy.

Exploitation

• CISA SSVC: exploitation none, automatable no, technical impact partial
• No public proof-of-concept code and no known exploitation in the wild found at the time of research
• CISA KEV: not listed

Our recommendation

• Check whether any Zebra node or Zcash infrastructure is operated in your environment
• Upgrade zebrad to 4.4.1 or later and zebra-script to 6.0.1 or later immediately
• After the upgrade, verify that the node is on the same chain as the wider Zcash network
• Typical SME IT (Windows, Microsoft 365, office network) is not affected unless Zebra is in use
• Note: the CVSS severity differs between sources (CVE record 8.3, GitHub 9.3); treat it as high priority where Zebra is deployed

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• GitHub Security Advisory GHSA-pvmv-cwg8-v6c8 github.com
• VulnCheck advisory www.vulncheck.com
• OSV entry CVE-2026-104435 osv.dev
• Zebra 4.4.1 release github.com
• Strix CVE-2026-104435 www.strix.ai

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 14:22.