CVE-2026-33471
nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | nimiq-block | < 1.3.0 | 1.7.2 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nimiq | Nimiq Proof-Of-Stake | before 1.3.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-6973-8887-87ff
- https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff
- https://github.com/nimiq/core-rs-albatross/pull/3657
- https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823
- https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0
- https://nvd.nist.gov/vuln/detail/CVE-2026-33471