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CVE-2026-33471 — Vulnerability in nimiq-block — CVE Details

CRITICAL

nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation

Published April 22, 2026Updated May 5, 2026Source: osv

Summary

### Impact `SkipBlockProof::verify` computes its quorum check using `BitSet.len()`, then iterates `BitSet` indices and casts each `usize` index to `u16` (`slot as u16`) for slot lookup. If an attacker can get a `SkipBlockProof` verified where `MultiSignature.signers` contains out-of-range indices spaced by 65536, these indices inflate `len()` but collide onto the same in-range `u16` slot during aggregation. This makes it possible for a malicious validator with far fewer than `2f+1` real signer slots to pass skip block proof verification by multiplying a single BLS signature by the same factor. ### Patches [The patch for this vulnerability](https://github.com/nimiq/core-rs-albatross/pull/3657) is included as part of [v1.3.0](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0). ### Workarounds No known workarounds.

Advisory Timeline

  • First published April 22, 2026 (173 days ago).
  • Last revised May 5, 2026 — 13 days after initial publication.

Affected Packages (1)

Affects 1 ecosystem: crates.io (1).

PackageEcosystemAffectedFixed In
nimiq-block
crates.io
All versionsRange-based data available

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.6 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

References

Frequently Asked Questions

What is CVE-2026-33471?
nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.6/10).
How do I check if my project is affected by CVE-2026-33471?
CVE-2026-33471 affects nimiq-block. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-33471 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.6

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-6973-8887-87ff

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