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0xCERT Security Advisory 0xCERT-2026-0194
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Advisory-ID:  0xCERT-2026-0194
Severity:     Critical
Published:    2026-05-07T21:02:30.000Z
Updated:      2026-10-08T22:47:30.065Z
Chains:       n/a
URL:          https://www.0xcert.com/advisory/0xCERT-2026-0194

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

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

Details
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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.

Affected
- - zebrad (rust) < 4.4.0 — fixed in 4.4.0

Severity
Critical (CVSS 9.2), as rated by the upstream advisory.

Recommended actions
- - Upgrade zebrad to 4.4.0 or later

Source & attribution
This 0xCERT advisory summarises GHSA-cwfq-rfcr-8hmp from the GitHub Advisory Database, credited upstream to sangsoo-osec, defuse, mpguerra, upbqdn: https://github.com/advisories/GHSA-cwfq-rfcr-8hmp. Details may change; refer to the original source for the authoritative record.

References
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- - https://github.com/advisories/GHSA-cwfq-rfcr-8hmp
- - https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-cwfq-rfcr-8hmp
- - https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0

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