How severe is CVE-2026-34066?

CVE-2026-34066 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-34066 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34066?

CVE-2026-34066 affects Nimiq Nimiq Proof-of-stake. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34066?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34066 have an EU (EUVD) identifier?

Yes. CVE-2026-34066 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25064.

When was CVE-2026-34066 published?

CVE-2026-34066 was published on 2026-04-22 and last updated on 2026-06-17.

CVE-2026-34066

CVE-2026-34066 is a medium-severity vulnerability in Nimiq Nimiq Proof-of-stake with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-25064
Weakness: CWE-20
Affected product: Nimiq Nimiq Proof-of-stake
Published: 2026-04-22
Last modified: 2026-06-17

Description

nimiq-blockchain provides persistent block storage for Nimiq's Rust implementation. Prior to version 1.3.0, `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 patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.

Frequently asked questions

What is CVE-2026-34066?: nimiq-blockchain provides persistent block storage for Nimiq's Rust implementation. Prior to version 1.3.0, `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 patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.
How severe is CVE-2026-34066?: CVE-2026-34066 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-34066 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34066?: CVE-2026-34066 affects Nimiq Nimiq Proof-of-stake. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34066?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34066 have an EU (EUVD) identifier?: Yes. CVE-2026-34066 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25064.
When was CVE-2026-34066 published?: CVE-2026-34066 was published on 2026-04-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nimiq:nimiq_proof-of-stake:*:*:*:*:*:rust:*:*

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