Zebra's Transparent SIGHASH_SINGLE Handling Diverges from zcashd for Corresponding Outputs

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.2 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Zebra Transparent SIGHASHSINGLE Corresponding-Output Handling Diverges From zcashd Summary For V5+ transparent spends, Zebra and zcashd disagree on the same consensus rule: SIGHASHSINGLE must fail when the input index has no corresponding output. zcashd treats this as consensus-invalid under ZIP-244, while Zebra's transparent verification path computes a digest for the missing-output case instead of failing. The result is a direct block-validity split. A malformed V5 transparent transaction can be accepted by Zebra, retained in Zebra's mempool, selected into Zebra getblocktemplate, mined into a block, and then rejected by zcashd. Details Validated code revisions used during analysis: - zcashd: 2c63e9aa08cb170b0feb374161bea94720c3e1f5 - Zebra: a905fa19e3a91c7b4ead331e2709e6dec5db12cb Scope note: - earlier triage material grouped pre-V5 and V5 behavior together; - re-execution on the pinned revisions did not reproduce the claimed pre-V5 / V4 reject-side behavior; - this advisory…

Published by the source

7 May 2026, 21:02 UTC

Last modified by the source

18 May 2026, 17:04 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cwfq-rfcr-8hmp

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# Patch Next advisory brief: GHSA-cwfq-rfcr-8hmp

Advisory: Zebra's Transparent SIGHASH_SINGLE Handling Diverges from zcashd for Corresponding Outputs
IDs: GHSA-cwfq-rfcr-8hmp
Record: https://patchnext.com/advisories/ghsa-cwfq-rfcr-8hmp (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zebrad 4.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io zebrad: affected < 4.4.0; fixed in 4.4.0

## Suggested inspection (read-only)
- crates.io zebrad: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on zebrad.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cwfq-rfcr-8hmp (GitHub-reviewed advisory GHSA-cwfq-rfcr-8hmp lists affected ranges: crates.io zebrad >=0 <4.4.0)

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