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Nimiq light-blockchain: Light blockchain rebranch issue

Type: advisorySources: OSV

Nimiq is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.4.0, when LightBlockchain::rebranch() adopts a fork chain whose tip is a macro block (checkpoint or election), it only updates self.head but fails to update self.macro_head, self.election_head, self.current_validators, or store the election header in the chain_store. This is in direct contrast with the full Blockchain::rebranch() at blockchain/src/blockchain/push.rs:504-518, which correctly updates all macro/election state when the new head is a macro block. After a rebranch to a macro block, the stale macro_head causes subsequent macro blocks pushed via push() to be verified against the wrong predecessor via verify_macro_successor(&this.macro_head). If the rebranch target was an election block, the stale current_validators causes every subsequent block to fail verify_validators(), completely stalling the light client's chain progression. This issue has been patched in version 1.4.0.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-46540
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 15:49 UTC · Revision 1

Source evidence

Nimiq light-blockchain: Light blockchain rebranch issue

core-osv · Original source

Published 9 Jun 2026, 23:45 UTC

Nimiq is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.4.0, when LightBlockchain::rebranch() adopts a fork chain whose tip is a macro block (checkpoint or election), it only updates self.head but fails to update self.macro_head, self.election_head, self.current_validators, or store the election header in the chain_store. This is in direct contrast with the full Blockchain::rebranch() at blockchain/src/blockchain/push.rs:504-518, which correctly updates all macro/election state when the new head is a macro block. After a rebranch to a macro block, the stale macro_head causes subsequent macro blocks pushed via push() to be verified against the wrong predecessor via verify_macro_successor(&this.macro_head). If the rebranch target was an election block, the stale current_validators causes every subsequent block to fail verify_validators(), completely stalling the light client's chain progression. This issue has been patched in version 1.4.0.

osv:CVE-2026-46540
Complete source record
{
  "id": "f66d77a093ba36b1c01a1f7a712331b4c5a23f39210cc557ee256bb9bf507a6d",
  "url": "https://osv.dev/vulnerability/CVE-2026-46540",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Nimiq light-blockchain: Light blockchain rebranch issue",
    "summary": "Nimiq is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.4.0, when LightBlockchain::rebranch() adopts a fork chain whose tip is a macro block (checkpoint or election), it only updates self.head but fails to update self.macro_head, self.election_head, self.current_validators, or store the election header in the chain_store. This is in direct contrast with the full Blockchain::rebranch() at blockchain/src/blockchain/push.rs:504-518, which correctly updates all macro/election state when the new head is a macro block. After a rebranch to a macro block, the stale macro_head causes subsequent macro blocks pushed via push() to be verified against the wrong predecessor via verify_macro_successor(&this.macro_head). If the rebranch target was an election block, the stale current_validators causes every subsequent block to fail verify_validators(), completely stalling the light client's chain progression. This issue has been patched in version 1.4.0.",
    "evidence": "osv:CVE-2026-46540",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-46540",
      "aliases": [
        "CVE-2026-46540",
        "GHSA-m3pg-qc2q-mg8c"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nimiq/core-rs-albatross",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "e156ecc4a14377eb3e4b71f340a8ae905b9864b2"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.4.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e156ecc4a14377eb3e4b71f340a8ae905b9864b2"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v1.4.0"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.4.0"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.3.0",
            "v1.2.2",
            "v1.2.1",
            "v1.2.0",
            "v1.1.1",
            "v1.1.0",
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            "v1.0.0",
            "v1.0.0-rc.5",
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            "v1.0.0-rc.3",
            "v1.0.0-rc.2",
            "v1.0.0-rc.1",
            "v1.0.0-rc.0",
            "v0.24.4",
            "v0.24.3",
            "v0.24.2",
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            "v0.22.2",
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            "v0.22.0",
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            "v0.20.5",
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            "v0.20.3",
            "v0.20.2",
            "v0.20.1",
            "v0.20.0",
            "v0.19.0",
            "v0.18.0",
            "v0.17.0",
            "v0.16.1",
            "v0.16.0",
            "v0.15.0",
            "v0.14.0",
            "v0.13.1",
            "v0.13.0",
            "v0.12.1",
            "v0.12.0",
            "v0.11.5",
            "v0.11.4",
            "v0.11.3",
            "v0.11.2",
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            "v0.11.0",
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            "v0.4.1",
            "v0.4.0",
            "v0.3.3",
            "v0.3.2",
            "v0.3.1",
            "v0.3.0",
            "v0.2.2",
            "v0.2.1",
            "v0.2.0",
            "v0.1.0",
            "v0.1.0-rc.3",
            "v0.1.0-rc.2",
            "v0.1.0-rc.1",
            "v0.1.0-rc.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-46540.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.206594057Z",
      "provider": "osv",
      "references": [
        "https://github.com/nimiq/core-rs-albatross/releases/tag/v1.4.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46540.json",
        "https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-m3pg-qc2q-mg8c",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-46540",
        "https://github.com/nimiq/core-rs-albatross/pull/3706"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-841"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46540.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-46540",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504274,
  "published_at": "2026-06-09T23:45:01.847+00:00"
}