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

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- bitcoinjs / bitcoinjs-lib: >= 2.3.0, < 5.2.1 (affected); >= 6.0.0, < 6.1.8 (affected); >= 7.0.0-rc.0, < 7.0.2 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 4.0: 9.3 (critical); 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; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-354

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gpw6 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/bitcoinjs/bitcoinjs-lib/commit/009f165edfbf925cad8964b2dce478d18dd19449 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/bitcoinjs/bitcoinjs-lib/commit/b79c7714c0687473dc6e25c69fc5fc597302c7a0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/bitcoinjs/bitcoinjs-lib/commit/f3434d1e4bb5e0784fe769c4cd08a243576232a1 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-107846; retrieved 2026-11-04; source updated 2026-11-04

Revision: b3a9ff9d1df2524bc55863f32e2f321b0aaae9ffe3cae5a8246eae73c13ca78d

Canonical: https://y2.dev/cve/CVE-2026-107846

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