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CVE-2026-46539 nimiq CVE debrief

CVE-2026-46539 is a MEDIUM severity vulnerability in Nimiq's Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. A logic flaw in BlockInclusionProof::is_block_proven causes the function to return true without performing any cryptographic verification when get_interlink_hops yields an empty hop list. This occurs when the target block is at the election block position immediately preceding the election head's epoch. An attacker providing transaction inclusion proofs can forge a MacroBlock header for that epoch position and have it accepted as 'proven' without any hash or signature verification. This issue has been patched in version 1.4.0.

Vendor
nimiq
Product
core-rs-albatross
CVSS
MEDIUM 5.9
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 Nimiq Proof-of-Stake protocol, specifically those using versions prior to 1.4.0, should be aware of this vulnerability and take steps to update to the patched version.

Technical summary

The vulnerability is caused by a logic flaw in the BlockInclusionProof::is_block_proven function. When get_interlink_hops yields an empty hop list, the function returns true without performing any cryptographic verification. This can occur when the target block is at the election block position immediately preceding the election head's epoch. An attacker can exploit this vulnerability by providing transaction inclusion proofs to forge a MacroBlock header for that epoch position, which can be accepted as 'proven' without any hash or signature verification.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update to version 1.4.0 or later
  • Review and verify transaction inclusion proofs

Evidence notes

The vulnerability has been patched in version 1.4.0. Users should update to this version or later to mitigate the vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46539 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46539

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

  • CVE-2026-46539 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46539

    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.