{"id":"CVE-2026-33471","aliases":["GHSA-6973-8887-87ff"],"url":"https://o3.security/vulnerability/CVE-2026-33471","summary":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation","details":"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.","published":"2026-04-22T19:13:04.687Z","modified":"2026-08-12T03:51:14.737147147Z","cvss":{"score":9.6,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H"},"epss":{"score":0.00217,"percentile":0.12331,"asOf":"2026-08-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"nimiq-block","fixedVersion":null}],"fix":{"url":"https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823","label":"nimiq/core-rs-albatross@d020590"},"references":[{"type":"WEB","url":"https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33471.json"},{"type":"ADVISORY","url":"https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33471"},{"type":"FIX","url":"https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823"},{"type":"WEB","url":"https://github.com/nimiq/core-rs-albatross/pull/3657"},{"type":"PACKAGE","url":"https://github.com/nimiq/core-rs-albatross"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:14.737147147Z"}}