{"id":"CVE-2026-33471","aliases":["GHSA-6973-8887-87ff"],"title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation","summary":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices & u16 truncation","severity":"critical","cvss":9.6,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","vendor":"nimiq-block","product":"nimiq-block","ecosystem":"rust","affected":["nimiq-block < 1.7.2"],"patched":["nimiq-block 1.7.2"],"published":"2026-04-22","updated":"2026-10-30","sourceUpdated":"2026-10-30T15:45:11.536013768Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-6973-8887-87ff","references":[{"url":"https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33471"},{"url":"https://github.com/nimiq/core-rs-albatross/pull/3657"},{"url":"https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823"},{"url":"https://github.com/nimiq/core-rs-albatross"},{"url":"https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0"},{"url":"https://github.com/advisories/GHSA-6973-8887-87ff"}],"tags":["osv","rust","ghsa"],"epss":0.00217,"epssPercentile":0.12261,"cwe":["CWE-20","CWE-190","CWE-345","CWE-1284"],"ingestedAt":"2026-10-30T16:03:45.844Z","slug":"CVE-2026-33471","body":"## Overview\n\n### Impact\n`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.\n\nThis 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.\n\n### Patches\n[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).\n\n### Workarounds\nNo known workarounds.\n\n## Affected packages\n\n- `nimiq-block < 1.7.2`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `nimiq-block 1.7.2`","depth":"midnight","depthScore":53,"depthScoreParts":{"impact":52.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}