{"id":"CVE-2026-33471","aliases":["EUVD-2026-25054","GHSA-6973-8887-87ff"],"status":"published","title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation","description":"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.","severity":{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00217,"percentile":0.12344,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1284","CWE-190","CWE-20","CWE-345"],"published":"2026-04-22T19:13:04Z","modified":"2026-10-30T15:45:11Z","fixes":[{"ecosystem":"crates.io","package":"nimiq-block","fixed_in":["1.3.0","1.7.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"nimiq-block","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0"}]}]},{"source":"osv","ecosystem":"crates.io","package":"nimiq-block","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.7.2"}]}]}],"products":[{"vendor":"nimiq","product":"nimiq-block"},{"vendor":"nimiq","product":"nimiq_proof-of-stake"}],"references":[{"url":"https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff","tags":["x_refsource_CONFIRM","Patch","Vendor Advisory","advisory","web"]},{"url":"https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://github.com/nimiq/core-rs-albatross/pull/3657","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33471","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-6973-8887-87ff"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33471.json","tags":["advisory"]},{"url":"https://github.com/nimiq/core-rs-albatross","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-33471","title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation","description":"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.","status":"published","published":"2026-04-22T19:13:04.687Z","modified":"2026-04-23T14:15:20.57Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-20","CWE-190","CWE-345","CWE-1284"],"updated_at":"2026-11-02T14:20:08.009733Z"}],"euvd":[{"id":"EUVD-2026-25054","description":"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.","status":"published","published":"2026-04-22T19:13:04Z","modified":"2026-04-23T14:15:20Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T19:24:19.171803Z"}],"ghsa":[{"id":"GHSA-6973-8887-87ff","title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation","description":"### 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.","status":"published","published":"2026-04-22T19:13:47Z","modified":"2026-10-30T15:35:33Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical"}],"cwes":["CWE-20","CWE-190","CWE-345","CWE-1284"],"updated_at":"2026-11-02T14:41:41.028239Z"}],"nvd":[{"id":"CVE-2026-33471","description":"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.","status":"published","published":"2026-04-22T20:16:40.317Z","modified":"2026-10-26T21:10:00.17Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-20","CWE-190","CWE-345","CWE-1284"],"updated_at":"2026-11-02T14:12:15.867234Z"}],"osv":[{"id":"CVE-2026-33471","title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation","description":"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.","status":"published","published":"2026-04-22T19:13:04.687Z","modified":"2026-10-28T02:30:30.754137873Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical"}],"cwes":["CWE-1284","CWE-190","CWE-20","CWE-345"],"updated_at":"2026-11-02T15:45:01.896044Z"},{"id":"GHSA-6973-8887-87ff","title":"nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation","description":"### 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.","status":"published","published":"2026-04-22T19:13:47Z","modified":"2026-10-30T15:45:11.536013768Z","cvss":[{"version":"3.1","score":9.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H","level":"critical"}],"cwes":["CWE-1284","CWE-190","CWE-20","CWE-345"],"updated_at":"2026-11-02T15:46:39.618611Z"}]}}