GHSA-8m29-fpq5-89jj is a critical-severity (CVSS 9.1) CWE-573 vulnerability in zebrad. O3 Security confirms whether GHSA-8m29-fpq5-89jj is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Zebra Vulnerable to Consensus Divergence in Transparent Sighash Hash-Type Handling
Real-World Exposure
zebrad🦀zebra-scriptReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
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
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
All Zebra versions prior to version 4.3.1. (Some older versions are not impacted but are no longer supported by the network.)
Description
Verification of transparent transactions inherits the Bitcoin Script verification code in C++. Since it is consensus-critical, this code was called from Zebra through foreign function interface (FFI). That interface was clunky because it required parsing the whole transaction in C++ code, which would then pull Rust libraries which could get in conflict with Zebra code. A refactoring was done so that only the verification itself was done in C++, and the rest done by Rust code, using a callback. However, in this refactoring, it was not noticed that a particular consensus rule - only accepting known hash types in transparent transaction signatures - was being enforced in C++ code and thus had to be enforced by the Rust caller.
An attacker could exploit this by:
- Submitting a V4 or V5 transaction with an invalid hash type
- The V5 transaction would be accepted by Zebra nodes but not by
zcashdnodes (and vice-versa for V4), creating a consensus split in the network.
Impact
Consensus Failure
- Attack Vector: Network.
- Effect: Network partition/consensus split.
- Scope: Any Zebra affected Zebra node
Fixed Versions
This issue is fixed in Zebra 4.3.1.
The fix adds the consensus check in the caller of the C++ verification code. It also uses the raw hash type for V4 sighash computations.
Mitigation
Users should upgrade to Zebra 4.3.1 or later immediately.
There are no known workarounds for this issue. Immediate upgrade is the only way to ensure the node remains on the correct consensus path and is protected against malicious chain forks.
Credits
Thanks Alex “Scalar” Sol for finding and reporting the issue, and to @sangsoo-osec who independently found the same issue and demonstrated that the V4 variant was also exploitable.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | zebrad | all versions | 4.3.1 |
| 🦀crates.io | zebra-script | all versions | 5.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zebrad. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update zebrad to 4.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8m29-fpq5-89jj is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-8m29-fpq5-89jj is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-8m29-fpq5-89jj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-8m29-fpq5-89jj in your dependencies?
O3 detects GHSA-8m29-fpq5-89jj across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.