Critical 9.6Published Apr 22, 2026

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

Updated under an hour ago (Oct 27, 2026, 1:23 PM ET)

Does this affect you?

It affects nimiq-block and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for nimiq-block

Exploited in the last 30 days

nimiq-block contains block primitives to be used in Nimiq's Rust implementation. `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. Prior to version 1.3.0, 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. The patch for this vulnerability is included as part of v1.3.0. No known workarounds are available.

CVSS: 9.6 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
Weakness (CWE): CWE-20, CWE-190, CWE-345, CWE-1284
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Apr 23, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nimiq nimiq-block nimiq:block (from the name)	before 1.3.0	CNA record
nimiq nimiq_proof-of-stake nimiq:nimiq_proof-of-stake	before 1.3.0	NVD

References

References

https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff	x-refsource-confirm, patch, vendor-advisory
https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823	x-refsource-misc, patch
https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.