CVE-2026-33471

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data tampering, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-22 20:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-26 21:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 9.6 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-04-22 20:16 UTC

Last modified

2026-10-26 21:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Analyzed

Affected

• Nimiq proof-of-stake < 1.3.0

Attack profile CVSS 3.1 · 9.6

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-33471.md and follow it. Check whether this project is affected by CVE-2026-33471. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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