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

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Summary

CVECVE-2026-33471
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-22 20:16:40 UTC
Updated2026-04-22 21:23:52 UTC
Descriptionnimiq-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.

Risk And Classification

Primary CVSS: v3.1 9.6 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

Problem Types: CWE-20 | CWE-190 | CWE-345 | CWE-1284 | CWE-20 CWE-20: Improper Input Validation | CWE-190 CWE-190: Integer Overflow or Wraparound | CWE-345 CWE-345: Insufficient Verification of Data Authenticity | CWE-1284 CWE-1284: Improper Validation of Specified Quantity in Input

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.6CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
3.1CNADECLARED9.6CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nimiq Nimiq-block affected < 1.3.0 Not specified

References

ReferenceSourceLinkTags
github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0 [email protected] github.com
github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd6... [email protected] github.com
github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff [email protected] github.com
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