Integer overflow in Nimiq Nimiq-Block
CVE-2026-33471
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.002 (12.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H.
Affected products
- Nimiq Nimiq-block — versions < 1.3.0
- Nimiq Nimiq_proof-of-stake
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-33471?
- CVE-2026-33471 is a critical-severity vulnerability in Nimiq Nimiq-Block, classified under Improper Input Validation. CVSS score: 9.6/10. Published 2026-04-22.
- How severe is CVE-2026-33471?
- Critical severity. CVSS v3 base score is 9.6 out of 10.