PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-46540 nimiq CVE debrief

CVE-2026-46540 is a MEDIUM severity vulnerability in the Nimiq Proof-of-Stake protocol implementation. The issue arises from the LightBlockchain::rebranch() function not correctly updating certain state variables when adopting a fork chain with a macro block (checkpoint or election) as its tip. Specifically, it fails to update self.macro_head, self.election_head, self.current_validators, and does not store the election header in the chain_store. This discrepancy in behavior compared to the full Blockchain::rebranch() function can lead to subsequent macro blocks being verified against the wrong predecessor and cause chain progression issues. The vulnerability has been patched in version 1.4.0.

Vendor
nimiq
Product
core-rs-albatross
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-10
Original CVE updated
2026-06-10
Advisory published
2026-06-10
Advisory updated
2026-06-10

Who should care

Users of Nimiq's Rust implementation of the Albatross consensus algorithm, specifically those using versions prior to 1.4.0, should be aware of this vulnerability and take steps to update their implementation.

Technical summary

The LightBlockchain::rebranch() function in Nimiq's Rust implementation of the Albatross consensus algorithm fails to correctly update certain state variables when adopting a fork chain with a macro block as its tip. This can lead to subsequent macro blocks being verified against the wrong predecessor and cause chain progression issues.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update to version 1.4.0 or later of Nimiq's Rust implementation of the Albatross consensus algorithm.
  • Review and verify the implementation of LightBlockchain::rebranch() to ensure correct behavior.

Evidence notes

The vulnerability was patched in version 1.4.0. References to the patch and advisory can be found at [ref-5](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.4.0), [ref-6](https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-m3pg-qc2q-mg8c), and [ref-4](https://github.com/nimiq/core-rs-albatross/pull/3706).

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46540 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46540

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-46540 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46540

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.