CVE-2026-34066: Nimiq Proof-Of-Stake

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Nimiq Nimiq Proof-Of-Stake: before 1.3.0 (fixed in 1.3.0)

Published 2026-04-22. Last modified 2026-06-17.