CVE-2026-34068: nimiq-transaction UpdateValidator Transactions Allows Voting Key Vulnerability

MODERATE
Advisory Identifier: GHSA-pf4j-pf3w-95f9
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CVSS 6.8
CWE-347
Published
Advisory Summary

CVE-2026-34068 is a MODERATE (CVSS 6.8) updatevalidator transactions allows voting key vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting nimiq-transaction libraries in the crates.io ecosystem. The issue involves updatevalidator transactions allows voting key change without proof-of-knowledge. Remediation is available in the latest vendor maintenance releases.

CVE-2026-34068 at a Glance

CVE Identifier CVE-2026-34068
GHSA Identifier GHSA-pf4j-pf3w-95f9
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product nimiq-transaction
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 6.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-34068

To remediate this vulnerability, upgrade all affected nimiq-transaction dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

nimiq-transaction fixed: Latest secure release 
Upgrade nimiq-transaction to Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for nimiq-transaction

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-34068, inspect your project dependencies for nimiq-transaction:

inspect dependencies for nimiq-transaction

Analyze the terminal output to locate any version of nimiq-transaction in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In nimiq-transaction, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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](https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f) is included as part of [v1.3.0](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0). ### Workarounds No known workarounds.

CVE-2026-34068 Affected nimiq-transaction Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
nimiq-transaction
 crates.io
≤ 0.2.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-pf4j-pf3w-95f9
NVD — CVE-2026-34068 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34068
nimiq-transaction Source Repository REPOSITORY
https://github.com/nimiq/core-rs-albatross/pull/3654
Security Fix Commit FIX COMMIT
https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f
nimiq-transaction Source Repository REPOSITORY
https://github.com/nimiq/core-rs-albatross
nimiq-transaction Release RELEASE
https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0

Frequently Asked Questions

What is CVE-2026-34068?
CVE-2026-34068 is a security vulnerability in nimiq-transaction involving UpdateValidator transactions allows voting key change without proof-of-knowledge under CWE-347: Improper Verification of Cryptographic Signature.
Which nimiq-transaction versions are affected?
Affected versions include releases prior to current release patches across affected packages: nimiq-transaction.
What version fixes CVE-2026-34068?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is nimiq-transaction affected?
Yes, nimiq-transaction is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-34068?
CVE-2026-34068 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2026-34068?
CVE-2026-34068 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check crates.io dependencies for CVE-2026-34068?
Run the dependency tree command: 'inspect dependencies for nimiq-transaction'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pf4j-pf3w-95f9",
  "modified" : "2026-04-27T16:22:49Z",
  "published" : "2026-04-22T19:22:53Z",
  "aliases" : [ "CVE-2026-34068" ],
  "summary" : "nimiq-transaction: UpdateValidator transactions allows voting key change without proof-of-knowledge",
  "details" : "### Impact\nThe 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.\n\nBecause 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.\n\nWhile 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.\n\n### Patches\n[The patch for this vulnerability](https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f) is included as part of [v1.3.0](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0).\n\n### Workarounds\nNo known workarounds.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "nimiq-transaction"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-pf4j-pf3w-95f9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34068"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nimiq/core-rs-albatross/pull/3654"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nimiq/core-rs-albatross/commit/e7f0ab7d2115e17d6e5548ddc60f10df1a5d645f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nimiq/core-rs-albatross"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-22T19:22:53Z",
    "nvd_published_at" : "2026-04-22T21:17:08Z"
  }
}