CVE-2026-34068 nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-knowledge
An attacker could potentially forge quorum justifications by bypassing proof-of-knowledge checks in validator updates, compromising consensus integrity.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-34068?
CVE-2026-34068 is a medium-severity vulnerability in nimiq-transaction, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
nimiq-transaction provides the transaction primitive to be used in Nimiq's Rust implementation. Prior to version 1.3.0, the staking contract accepts `UpdateValidator` transactions that set `new_voting_key=Some(...)` while omitting `new_proof_of_knowledge`. this skips the proof-of-knowledge requirement that is needed to prevent BLS rogue-key attacks when public keys are aggregated. Because tendermint macro block justification verification aggregates validator voting keys and verifies a single aggregated BLS signature against that aggregate public key, a rogue-key voting key in the validator set can allow an attacker to forge a quorum-looking justification while only producing a single signature. While the impact is critical, the exploitability is low: The voting keys are fixed for the epoch, so the attacker would need to know the next epoch validator set (chosen through VRF), which is unlikely. The patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.
Weakness: CWE-347
Which versions are affected by CVE-2026-34068?
2 open source packages ship an affected version, including nimiq-transaction. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
nimiq-transaction crates.io | All versions to 0.2.0 | None |
nimiq-transaction crates.io | All versions to 0.2.0 | None |
Products include Nimiq Nimiq Proof-of-Stake.
How do I fix CVE-2026-34068?
No fix has been published for CVE-2026-34068 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-34068 being exploited?
There is no known exploitation of CVE-2026-34068 in the wild and no public exploit code.
Other vulnerabilities in nimiq-transaction
- CVE-2026-33471 nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation
- CVE-2026-40093 nimiq-blockchain is missing a wall-clock upper bound on block timestamps
- CVE-2026-34063 network-libp2p: Peer can crash the node by opening discovery protocol substream twice
- CVE-2026-34065 nimiq-primitives: Node crash due to missing interlink validation in election macro block proposals
- CVE-2026-32605 Nimiq: Remote crash via off-by-one signer bounds check in proposal buffer
Sources
Also known as GHSA-pf4j-pf3w-95f9.