CVE-2026-34068

// Conceptual PoC demonstrating the vulnerable transaction structure // This is pseudo-code based on the vulnerability description struct UpdateValidatorTransaction { validator_id: Address, new_voting_key: Option<PublicKey>, new_proof_of_knowledge: Option<Proof>, // ... other fields } fn main() { // Attacker generates a malicious key pair let (malicious_pub_key, _) = generate_bls_keys(); // Construct a transaction with the new key but OMIT the proof of knowledge let vulnerable_tx = UpdateValidatorTransaction { validator_id: attacker_address, new_voting_key: Some(malicious_pub_key), // Key is set new_proof_of_knowledge: None, // VULNERABILITY: Proof is missing but accepted }; // In vulnerable versions (< 1.3.0), submitting this transaction // adds the rogue key to the validator set. submit_transaction(vulnerable_tx); }

{"cve": {"id": "CVE-2026-34068", "sourceIdentifier": "[email protected]", "published": "2026-04-22T21:17:08.197", "lastModified": "2026-04-24T17:10:07.777", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N", "baseScore": 6.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 4.0}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-347"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nimiq:nimiq_proof-of-stake:*:*:*:*:*:rust:*:*", "versionEndExcluding": "1.3.0", "matchCriteriaId": "CD0CAAD1-7626-4A4A-A6F8-9DC46FE50731"}]}]}], "references": [{"url": "https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/nimiq/core-rs-albatross/pull/3654", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-pf4j-pf3w-95f9", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}]}}