Summary
Workarounds
No known workarounds.
Impact
HistoryStore::put_historic_txns uses an assert! to enforce invariants about HistoricTransaction.block_number (must be within the macro block being pushed and within the same epoch). During history sync, a peer can influence the history: &[HistoricTransaction] input passed into Blockchain::push_history_sync, and a malformed history list can violate these invariants and trigger a panic.
extend_history_sync calls this.history_store.add_to_history(..) before comparing the computed history root against the macro block header (block.history_root()), so the panic can happen before later rejection checks run.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2026-34066 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The patch for this vulnerability is included as part of v1.3.0.
Frequently Asked Questions
- What is CVE-2026-34066? CVE-2026-34066 is a medium-severity improper input validation vulnerability in nimiq-blockchain (rust), affecting versions <= 0.2.0. No fixed version is listed yet. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2026-34066? CVE-2026-34066 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of nimiq-blockchain are affected by CVE-2026-34066? nimiq-blockchain (rust) versions <= 0.2.0 is affected.
- Is there a fix for CVE-2026-34066? No fixed version is listed for CVE-2026-34066 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-34066 exploitable, and should I be worried? Whether CVE-2026-34066 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-34066 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-34066? No fixed version is listed yet. In the interim: Validate all external input against an allowlist of expected values, types, and ranges before processing.