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9.3
CVE-2026-107846: bitcoinjs-lib can accept duplicated transactions in a block
CVE-2026-107846 · published today
Summary
The Bitcoin JavaScript library bitcoinjs‑lib (versions before 5.2.1, 6.1.8 and 7.0.2) does not notice when a block’s transaction list contains duplicate entries. Because the duplicate entries produce the same block fingerprint, a malicious peer can add extra copies of a transaction without changing the block’s hash, causing tools that rely on the library to process the same transaction twice or to reject a valid block. Updating to the latest released versions of the library fixes the issue.
What to do
The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.
Affected software
| Vendor | Product | Affected versions |
|---|---|---|
| bitcoinjs | bitcoinjs-lib | >= 2.3.0, < 5.2.1 |
Original advisory text
bitcoinjs-lib: Undetected merkle node duplication in block root computation validates a forged transaction list
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/bitcoinjs/bitcoinjs-lib/commit/009f165edfbf925cad8964b2dce478... x_refsource_MISC
- https://github.com/bitcoinjs/bitcoinjs-lib/commit/b79c7714c0687473dc6e25c69fc5fc... x_refsource_MISC
- https://github.com/bitcoinjs/bitcoinjs-lib/commit/f3434d1e4bb5e0784fe769c4cd08a2... x_refsource_MISC
- https://github.com/bitcoinjs/bitcoinjs-lib/security/advisories/GHSA-8vv3-6qpc-gp... x_refsource_CONFIRM
Internet-facing
14 days
Internal
60 days
- Not known to be exploited
- Can be exploited automatically (estimated)
- Gives an attacker partial control (estimated)
Type
CWE-354Improper Validation of Integrity Check Value
Timeline
Published4 Nov 2026
Updated4 Nov 2026
First seen4 Nov 2026
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