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.
History

Fri, 06 Nov 2026 22:00:00 +0000

Type Values Removed Values Added
First Time appeared Bitcoinjs
Bitcoinjs bitcoinjs-lib
Vendors & Products Bitcoinjs
Bitcoinjs bitcoinjs-lib

Wed, 04 Nov 2026 19:15:00 +0000

Type Values Removed Values Added
Description 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.
Title bitcoinjs-lib: Undetected merkle node duplication in block root computation validates a forged transaction list
Weaknesses CWE-354
References
Metrics cvssV4_0

{'score': 9.3, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-11-04T19:02:39.453Z

Updated: 2026-11-04T19:02:39.453Z

Reserved: 2026-10-08T22:34:49.291Z

Link: CVE-2026-107846

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-04T19:17:18.130

Modified: 2026-11-04T19:17:18.130

Link: CVE-2026-107846

cve-icon Redhat

No data.