CVE-2026-41583: Zebra Vulnerable to Consensus Divergence in Transparent Sighash Hash-Type Handling

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.5%, percentile 40: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 40% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes zebrad (crates.io (Rust)) < 4.3.1, fixed in 4.3.1; zebra-script (crates.io (Rust)) < 5.0.2, fixed in 5.0.2. Check your lockfile, including transitive dependencies.

What it is

ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.3.1 and prior to zebra-script version 5.0.2, after a refactoring, Zebra failed to validate a consensus rule that restricted the possible values of sighash hash types for V5 transactions which were enabled in the NU5 network upgrade. Zebra nodes could thus accept and eventually mine a block that would be considered invalid by zcashd nodes, creating a consensus split between Zebra and zcashd nodes. In a similar vein, for V4 transactions, Zebra mistakenly used the "canonical" hash type when computing the sighash while zcashd (correctly per the spec) uses the raw value, which could also crate a consensus split. This issue has been patched in zebrad version 4.3.1 and zebra-script version 5.0.2.

From the GitHub advisory

CVE-2026-41583: Consensus Divergence in Transparent Sighash Hash-Type Handling

Summary

After a refactoring, Zebra failed to validate a consensus rule that restricted the possible values of sighash hash types for V5 transactions which were enabled in the NU5 network upgrade. Zebra nodes could thus accept and eventually mine a block that would be considered invalid by zcashd nodes, creating a consensus split between Zebra and zcashd nodes.

In a similar vein, for V4 transactions, Zebra mistakenly used the "canonical" hash type when computing the sighash while zcashd (correctly per the spec) uses the raw value, which could also crate a consensus split.

Severity

Weakness type: CWE-573.

Product: zebrad (crates.io (Rust)) · Assigned by: GitHub_M · Published: 2026-05-08

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.47% probability of exploitation activity in the next 30 days; percentile 40.

Timeline

• 2026-04-18 — GitHub-reviewed advisory GHSA-8m29-fpq5-89jj published (critical)
• 2026-05-08 — CVE record last updated
• 2026-05-08 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-8m29-fpq5-89jj github.com
2. CVE.org record CVE-2026-41583 cve.org
3. NVD entry CVE-2026-41583 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

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