CVE-2026-107846

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CVE-2026-107846

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

Details: 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.

References: https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107846.json, https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gpw6, 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