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0xCERT Security Advisory 0xCERT-2026-0307
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Advisory-ID:  0xCERT-2026-0307
Severity:     Critical
Published:    2026-11-04T19:17:18.130Z
Updated:      2026-11-04T20:08:04.629Z
Chains:       Bitcoin
URL:          https://www.0xcert.com/advisory/0xCERT-2026-0307

Title: CVE-2026-107846: bitcoinjs-lib

Summary
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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 re…

Details
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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 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.

Severity
Critical (CVSS 9.3), as scored by NVD.

Weakness
- - CWE-354

Recommended actions
- - Check whether you run or depend on the affected component and version
- - Apply the vendor's fix or mitigation from the references below

Source & attribution
This 0xCERT advisory summarises CVE-2026-107846 from the U.S. National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2026-107846. Details may change; refer to the original source for the authoritative record.

References
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- - https://nvd.nist.gov/vuln/detail/CVE-2026-107846
- - https://github.com/bitcoinjs/bitcoinjs-lib/commit/009f165edfbf925cad8964b2dce478d18dd19449
- - https://github.com/bitcoinjs/bitcoinjs-lib/commit/b79c7714c0687473dc6e25c69fc5fc597302c7a0
- - https://github.com/bitcoinjs/bitcoinjs-lib/commit/f3434d1e4bb5e0784fe769c4cd08a243576232a1
- - https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gpw6

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