CVE-2026-33471

// Conceptual PoC for CVE-2026-33471 // Demonstrates the index collision when casting usize to u16 fn main() { // Simulate the vulnerability: indices spaced by 65536 let index1: usize = 0; let index2: usize = 65536; // 2^16 // Vulnerable casting logic found in SkipBlockProof::verify let slot1 = index1 as u16; let slot2 = index2 as u16; println!("Index 1: {} -> Slot {}", index1, slot1); println!("Index 2: {} -> Slot {}", index2, slot2); // Collision occurs here assert_eq!(slot1, slot2); // In the real vulnerability, this collision allows // inflating the quorum count (BitSet.len()) // while aggregating signatures into the same slot. // Result: Verification passes with insufficient real signers. }

{"cve": {"id": "CVE-2026-33471", "sourceIdentifier": "[email protected]", "published": "2026-04-22T20:16:40.317", "lastModified": "2026-04-24T17:11:40.037", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H", "baseScore": 9.6, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.1, "impactScore": 5.8}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-20"}, {"lang": "en", "value": "CWE-190"}, {"lang": "en", "value": "CWE-345"}, {"lang": "en", "value": "CWE-1284"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nimiq:nimiq_proof-of-stake:*:*:*:*:*:rust:*:*", "versionEndExcluding": "1.3.0", "matchCriteriaId": "CD0CAAD1-7626-4A4A-A6F8-9DC46FE50731"}]}]}], "references": [{"url": "https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff", "source": "[email protected]", "tags": ["Patch", "Vendor Advisory"]}]}}