GHSA-6973-8887-87ff

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

Source: GitHub Advisory Database (reviewed) Critical CVE-2026-33471

Packages

Ecosystem	Package	Affected	Fixed in
crates.io	nimiq-block	< 1.7.2	1.7.2

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact `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. 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. ### Patches [The patch for this vulnerability](https://github.com/nimiq/core-rs-albatross/pull/3657) is included as part of [v1.3.0](https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0). ### Workarounds No known workarounds.

References

External links from the advisory. They lead to third-party sites.