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Vulnerability · Published Nov 4, 2026 · Assigned by GitHub_M

CVE-2026-107846bitcoinjs-lib: Undetected merkle node duplication in block root computation validates a forged transaction list

Critical 9.3

In plain English

A critical-severity security flaw in bitcoinjs-lib from bitcoinjs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities).

Severity (CVSS 4.0)9.3Critical
Exploit odds (30 days)0.2%top 92.4% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

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

Weakness: CWE-354 · 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

References