Quarkslab, a leading cybersecurity firm, has completed the first public third-party security assessment of Bitcoin Core, the reference implementation of the Bitcoin network. The audit was mandated by the Open Source Technology Improvement Fund (OSTIF) and funded by Brink, marking a significant milestone in Bitcoin’s ongoing efforts to strengthen its decentralized infrastructure.
Quarkslab, under funding from Brink and coordination by OSTIF, has completed the first publicly disclosed third‑party security audit in Bitcoin Core’s history. The team focused on core components including the P2P network, mempool, chain management, and consensus. The audit…
— Wu Blockchain (@WuBlockchain) November 20, 2025
Focus on p2p layer and consensus security
The audit, conducted by Quarkslab experts Robin David, Nicolas Surbayrole, and Mihail Kirov between May and September 2025, focused on the peer-to-peer networking layer, mempool, chain and peer management, and consensus logic. Spanning 100 man-days, the assessment combined manual code review, dynamic testing, and advanced fuzzing techniques. The goal was to identify potential vulnerabilities while enhancing Bitcoin Core’s testing infrastructure with new fuzzing harnesses and experimental testing approaches.
Findings included two low-severity issues and 13 informational recommendations, none of which pose immediate security risks. The audit also delivered practical contributions, such as a test corpora to improve code coverage, a Docker image for ensemble fuzzing campaigns, non-regression utilities using Bitcoin tracepoints, and experimental fuzzing methods including differential testing. These tools aim to strengthen Bitcoin Core’s robustness and prepare it for future protocol upgrades and network growth.
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Supporting Bitcoin’s long-term security
Bitcoin Core, initially released by Satoshi Nakamoto in 2009, underpins trillions of dollars in decentralized value. With tens of thousands of nodes globally, any flaw could have systemic consequences. Quarkslab’s audit highlights the importance of third-party security verification and continuous improvement of testing strategies. OSTIF and Brink emphasized that while no critical issues were found, the assessment offers marginal gains in code safety and innovative testing approaches that may uncover deeper vulnerabilities over time.
The audit reinforces Bitcoin Core’s position as a secure, mature, and continuously improving foundation for the Bitcoin network. It sets a precedent for ongoing public security evaluations in the decentralized finance ecosystem.
Meanwhile, Bitcoin Core version 30.0 has already been released, introducing updates to node architecture, privacy features, and data capabilities, sparking debate within the community and marking a major milestone in the network’s evolution.
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