GHSA-pvmv-cwg8-v6c8: Zebra v4.4.0 still accepts V5 SIGHASH_SINGLE without a corresponding output

Should you act?

• Only if you depend on one of the packages below, directly or transitively, in a vulnerable version. Check your lockfile with cargo audit.
• No CVE has been assigned, so it will not appear in CVE-based scanners that ignore GitHub advisories. npm audit, pip-audit and Dependabot do read GitHub advisories.

Affected packages

Details

Consensus Divergence in V5 Transparent SIGHASHSINGLE With No Corresponding Output

Summary

Zebra failed to enforce a ZIP-244 consensus rule for V5 transparent transactions: when an input is signed with SIGHASHSINGLE and there is no transparent output at the same index as that input, validation must fail. Zebra instead asked the underlying sighash library to compute a digest, and that library produced a digest over an empty output set rather than failing. An attacker could craft a V5 transaction with more transparent inputs than outputs that Zebra accepts but zcashd rejects, creating a consensus split between Zebra and zcashd nodes.

A previous fix (GHSA-cwfq-rfcr-8hmp) addressed a closely related case in the same area of the code, but did not cover this specific one.

Severity

Critical - This is a Consensus Vulnerability that could allow a malicious party to induce network partitioning, service disruption, and potential double-spend attacks against affected nodes.

Note that the impact is currently alleviated by the fact that currently most miners run zcashd.

Affected Versions

CVSS: 9.3 (v4.0) CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:H

Sources and references

1. GitHub Advisory GHSA-pvmv-cwg8-v6c8 github.com
2. github.com github.com

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