---
id: CVE-2026-107846
title: >-
  bitcoinjs-lib: Undetected merkle node duplication in block root computation
  validates a forged transaction list
summary: >-
  bitcoinjs-lib is a JavaScript Bitcoin library for Node.js and browsers. From
  2.3.0 until 5.2.1, 6.1.8, and 7.0.2, fastMerkleRoot pads odd Merkle-tree
  levels by hashing the final node with itself but does not report adjacent
  duplicate has…
severity: critical
cvss: 9.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:H/SA:H'
cvssSource: cna
cwe:
  - CWE-354
vendor: bitcoinjs
product: bitcoinjs-lib
affected:
  - 'bitcoinjs-lib >= 2.3.0, < 5.2.1'
  - 'bitcoinjs-lib >= 6.0.0, < 6.1.8'
  - 'bitcoinjs-lib >= 7.0.0-rc.0, < 7.0.2'
published: '2026-11-04'
updated: '2026-11-04'
sourceUpdated: '2026-11-04T19:02:39.453Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-107846'
references:
  - url: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gpw6
    label: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gpw6
  - url: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/009f165edfbf925cad8964b2dce478d18dd19449
    label: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/009f165edfbf925cad8964b2dce478d18dd19449
  - url: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/b79c7714c0687473dc6e25c69fc5fc597302c7a0
    label: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/b79c7714c0687473dc6e25c69fc5fc597302c7a0
  - url: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/f3434d1e4bb5e0784fe769c4cd08a243576232a1
    label: >-
      https://github.com/bitcoinjs/bitcoinjs-lib/commit/f3434d1e4bb5e0784fe769c4cd08a243576232a1
tags:
  - cve.org
ingestedAt: '2026-11-05T21:36:00.517Z'
epss: 0.0018
epssPercentile: 0.07573
---

## Overview

bitcoinjs-lib is a JavaScript Bitcoin library for Node.js and browsers. From 2.3.0 until 5.2.1, 6.1.8, and 7.0.2, fastMerkleRoot pads odd Merkle-tree levels by hashing the final node with itself but does not report adjacent duplicate hashes. The affected block-root verifier was introduced as Block.checkMerkleRoot() alongside Block.calculateMerkleRoot(), while later versions expose validation through checkTxRoots() and __checkMerkleRoot; these validation paths can accept a recomputed root without checking for mutation. A peer can append duplicate transactions so a different transaction list retains the original Merkle root, block header, proof of work, and block identifier. Consumers that rely on block-root validation, including explorers, exchange indexers, or SPV clients, can process a duplicated transaction twice or blacklist the shared block hash and reject the honest block. This issue is fixed in versions 5.2.1, 6.1.8, and 7.0.2.

## Affected

- `bitcoinjs-lib >= 2.3.0, < 5.2.1`
- `bitcoinjs-lib >= 6.0.0, < 6.1.8`
- `bitcoinjs-lib >= 7.0.0-rc.0, < 7.0.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.