CVE-2026-34068

MediumCVSS 6.8

Published: 22/04/2026(UTC)Updated: 26/10/2026(UTC)Translated: 27/10/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.20%

10th percentile - higher than 10% of all known CVEs

Summary

nimiq-transaction prior to version 1.3.0 allows UpdateValidator transactions that set a new voting key without the required proof-of-knowledge. Skipping this requirement enables BLS rogue-key attacks on key aggregation, potentially allowing an attacker to forge a quorum-looking Tendermint block justification with a single signature. Exploitability is low because it requires knowledge of the next epoch validator set chosen via VRF.

Risk Assessment

In a worst-case scenario an attacker could forge a quorum-looking justification and influence consensus, undermining chain integrity. Practical risk is low due to the difficulty of predicting the future validator set, but the impact would be severe.

Recommendation

Upgrade nimiq-transaction to version 1.3.0 or later, which contains the fix. No workarounds are known, so updating is the only recommended action.

Other vulnerabilities in nimiq-transaction

CVE-2026-34067Low
In nimiq-transaction prior to version 1.3.0, HistoryTreeProof::verify panics on a malformed proof where history.len() != positions.len() due to assert_eq!. The proof object is derived from untrusted p2p responses (ResponseTransactionsProof.proof) and is attacker-controlled. A malicious peer could trigger a crash by returning a crafted inclusion proof.

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS