Authenticated quorum bypass via truncated signer indices
Published Apr 22, 2026 · Updated Apr 22, 2026
Improper signer validation in Nimiq nimiq-block before 1.3.0 allows remote authenticated users to bypass skip-block quorum checks. SkipBlockProof::verify counts out-of-range BitSet entries, then truncates their usize indices to u16, so indices spaced by 65,536 inflate the quorum while resolving to the same validator slot. A malicious validator can multiply one valid BLS signature to obtain acceptance with fewer than 2f+1 genuine signer slots, undermining consensus integrity and availability.
Summary
What happened
Improper signer validation in Nimiq nimiq-block before 1.3.0 allows remote authenticated users to bypass skip-block quorum checks. SkipBlockProof::verify counts out-of-range BitSet entries, then truncates their usize indices to u16, so indices spaced by 65,536 inflate the quorum while resolving to the same validator slot. A malicious validator can multiply one valid BLS signature to obtain acceptance with fewer than 2f+1 genuine signer slots, undermining consensus integrity and availability.
The record
- CVE
- CVE-2026-33471
- Published
- Apr 22, 2026
- Updated
- Apr 22, 2026
- Vendor
- Nimiq
- Product
- nimiq-block
- Classifications
- CWE-20, CWE-345, CWE-1284, CWE-190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 22, 2026CVE publishedPublication date reported by the CVE source.
- Apr 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.3.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo