EUVD-2026-25086
GHSA-pf4j-pf3w-95f9
CVSS VectorNVD
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
Lifecycle Timeline
1DescriptionNVD
Impact
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.
Patches
The patch for this vulnerability is included as part of v1.3.0.
Workarounds
No known workarounds.
AnalysisAI
The Nimiq staking contract accepts UpdateValidator transactions that omit proof-of-knowledge validation when updating voting keys, enabling rogue-key attacks against BLS signature aggregation used in Tendermint block justification. An attacker who can predict the next epoch's validator set could forge quorum-appearing block justifications with a single signature. …
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External POC / Exploit Code
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