CVE-2026-34202 — zebrad
CVE-2026-34202 is a Code Injection vulnerability in zebrad. A fix is available for zebrad — see the affected versions and patch details below.
Zebra node crash — V5 transaction hash panic (P2P reachable)
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34202.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
zebrad🦀zebra-chainReal-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
Remote Denial of Service via Crafted V5 Transactions
Summary
A vulnerability in Zebra's transaction processing logic allows a remote, unauthenticated attacker to cause a Zebra node to panic (crash). This is triggered by sending a specially crafted V5 transaction that passes initial deserialization but fails during transaction ID calculation.
Severity
Critical - This is a Remote Denial of Service (DoS) that requires no authentication and can be triggered by a single network message.
Affected Versions
All Zebra versions supporting V5 transactions (Network Upgrade 5 and later) prior to version 4.3.0.
Description
The vulnerability stems from Zebra lazily validating transaction fields that are eagerly validated in the librustzcash parsing logic used when Zebra computes transaction ids and auth digests for V5 transactions where Zebra panics if those computations fail.
PushTransaction messages with malformed V5 transactions are successfully deserialized as the zebra-chain Transaction type by the network codec, but when Zebra converts those transactions into internal types to compute the TxID expecting it to succeed, it triggers a panic/crash.
An attacker can trigger this crash by sending a single crafted tx message to a Zebra node's public P2P port. The same issue can be triggered via the sendrawtransaction RPC method.
Impact
Remote Denial of Service
- Attack Vector: Remote, unauthenticated.
- Effect: Immediate crash of the Zebra node.
- Scope: Any node with an open P2P port (default 8233) or exposed RPC interface is vulnerable.
Fixed Versions
This issue is fixed in Zebra 4.3.0.
The fix ensures that any transaction that would fail TxID calculation is rejected during the initial deserialization phase, and replaces internal panics with graceful error handling.
Mitigation
Users should upgrade to Zebra 4.3.0 or later immediately.
If an immediate upgrade is not possible, users should ensure their RPC port is not exposed to the Internet. However, the P2P port must remain closed or restricted to trusted peers to fully mitigate the risk, which may impact the node's ability to sync with the network.
Credits
Zebra thanks robustfengbin, who discovered this issue and reported it via coordinated disclosure process.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | zebrad | all versions | 4.3.0cargo update -p zebrad --precise 4.3.0 |
| 🦀crates.io | zebra-chain | all versions | 6.0.1cargo update -p zebra-chain --precise 6.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zebrad, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update zebrad to 4.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34202 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34202 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-34202. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34202 in your dependencies?
O3 Security finds CVE-2026-34202 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.