Skip to content

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

Moderate severity GitHub Reviewed Published Apr 22, 2026 in nimiq/core-rs-albatross • Updated Apr 27, 2026

Package

cargo nimiq-transaction (Rust)

Affected versions

<= 0.2.0

Patched versions

None

Description

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.

References

@jsdanielh jsdanielh published to nimiq/core-rs-albatross Apr 22, 2026
Published to the GitHub Advisory Database Apr 22, 2026
Reviewed Apr 22, 2026
Published by the National Vulnerability Database Apr 22, 2026
Last updated Apr 27, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(10th percentile)

Weaknesses

Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data. Learn more on MITRE.

CVE ID

CVE-2026-34068

GHSA ID

GHSA-pf4j-pf3w-95f9

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.