CVE-2026-34068 (GCVE-0-2026-34068)

Vulnerability from cvelistv5 – Published: 2026-04-22 19:55 – Updated: 2026-04-23 12:56
VLAI?
Title
nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-knowledge
Summary
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.
Severity ?
6.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
CWE
  • CWE-347 - Improper Verification of Cryptographic Signature
Assigner
References
Impacted products
Vendor Product Version
nimiq nimiq-transaction Affected: < 1.3.0
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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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