Vulnerability-Lookup

GHSA-6973-8887-87FF

Vulnerability from github – Published: 2026-04-22 19:13 – Updated: 2026-04-27 16:22

Summary

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

Details

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 is included as part of v1.3.0.

Workarounds

No known workarounds.

Severity

9.6 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "nimiq-block"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "0.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33471"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1284",
      "CWE-190",
      "CWE-20",
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T19:13:47Z",
    "nvd_published_at": "2026-04-22T20:16:40Z",
    "severity": "CRITICAL"
  },
  "details": "### 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.",
  "id": "GHSA-6973-8887-87ff",
  "modified": "2026-04-27T16:22:04Z",
  "published": "2026-04-22T19:13:47Z",
  "references": [
    {
      "type": "WEB",
      "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": "WEB",
      "url": "https://github.com/nimiq/core-rs-albatross/pull/3657"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nimiq/core-rs-albatross"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation"
}

CVE-2026-33471 (GCVE-0-2026-33471)

Vulnerability from cvelistv5 – Published: 2026-04-22 19:13 – Updated: 2026-04-23 14:15

Title

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

Summary

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

9.6 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-23 14:15 UTC

CWE

CWE-20 - Improper Input Validation
CWE-190 - Integer Overflow or Wraparound
CWE-345 - Insufficient Verification of Data Authenticity
CWE-1284 - Improper Validation of Specified Quantity in Input

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/nimiq/core-rs-albatross/securi…	x_refsource_CONFIRM
https://github.com/nimiq/core-rs-albatross/commit…	x_refsource_MISC
https://github.com/nimiq/core-rs-albatross/releas…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
nimiq	nimiq-block	Affected: < 1.3.0

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33471",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-23T14:15:09.611330Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
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        "providerMetadata": {
          "dateUpdated": "2026-04-23T14:15:20.570Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "nimiq-block",
          "vendor": "nimiq",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.3.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "nimiq-block contains block primitives to be used in Nimiq\u0027s 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": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 9.6,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
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              "lang": "en",
              "type": "CWE"
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              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-345",
              "description": "CWE-345: Insufficient Verification of Data Authenticity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-1284",
              "description": "CWE-1284: Improper Validation of Specified Quantity in Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-22T19:45:53.754Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff",
          "tags": [
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          ],
          "url": "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-6973-8887-87ff"
        },
        {
          "name": "https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823",
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          "url": "https://github.com/nimiq/core-rs-albatross/commit/d02059053181ed8ddad6b59a0adfd661ef5cd823"
        },
        {
          "name": "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.3.0",
          "tags": [
            "x_refsource_MISC"
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        }
      ],
      "source": {
        "advisory": "GHSA-6973-8887-87ff",
        "discovery": "UNKNOWN"
      },
      "title": "nimiq-block has skip block quorum bypass via out-of-range BitSet indices \u0026 u16 truncation"
    }
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  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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    "cveId": "CVE-2026-33471",
    "datePublished": "2026-04-22T19:13:04.687Z",
    "dateReserved": "2026-03-20T16:16:48.969Z",
    "dateUpdated": "2026-04-23T14:15:20.570Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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