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VulnerabilityPublished Updated

CVE-2026-33471: nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation

Affects nimiq-blockSource GCVE Database

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Authoritative record:CVE-2026-33471· Critical 9.6

Not known to be exploited · CVSS 9.6 Critical : upgrade to 1.7.2 as a priority.

Data as of 30 Oct 2026, 16:33 UTC

CVSS 3.1 base score
9.6Critical
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.7.2
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade nimiq-block to 1.7.2.

Affected software

ProductAffectedFixed in
crates.ionimiq-blockAffected
  • <1.7.2
Fixed in
  • 1.7.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### 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.

References

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