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Vulnerability · Published Apr 22, 2026 · Assigned by GitHub_M

CVE-2026-34068nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-knowledge

Medium 6.8

In plain English

A medium-severity security flaw in nimiq-transaction from nimiq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).

Severity (CVSS 3.1)6.8Medium
Exploit odds (30 days)0.2%top 89.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected products (as reported)

VendorProductVersions
nimiq nimiq-transaction < 1.3.0

Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

References