The independent review conducted by Quarkslab confirms the robustness of Bitcoin Core’s codebase.
Bitcoin Core, the most widely used implementation of the Bitcoin protocol, has successfully completed its first public security audit carried out by an independent third party. The analysis, performed by cybersecurity firm Quarkslab, found no critical, high, or medium-severity issues.
The four-month audit—funded by the non-profit organization Brink in collaboration with the Open Source Technology Improvement Fund (OSTIF)—involved three specialized Quarkslab engineers for a total of 100 workdays. Completed last September, the review focused primarily on the peer-to-peer networking layer, considered the system’s main attack surface.
The experts also examined adjacent components, including mempool management, blockchain state, transaction validation, and consensus logic. Before beginning the code review, two auditors worked directly with Brink engineers to gain a deep understanding of Bitcoin Core’s architecture and development practices.
The verification process combined manual code analysis, dynamic testing, and advanced fuzzing techniques—an automated methodology that stresses software by feeding it large volumes of random, unexpected, or malformed data. This multidimensional approach allowed the team to assess security from multiple angles.
As Brink clarified, the audit’s goal was not to certify the software but to “actively search for vulnerabilities, improve testing methodologies, and identify practical ways to strengthen the codebase.”
Quarkslab confirmed the absence of relevant security concerns. Only two low-severity issues were identified, along with 13 informational recommendations—none of which qualify as security vulnerabilities under Bitcoin Core’s criteria.
“No high-impact issues were found, but marginal gain was brought on existing fuzzing harnesses as well as new ones to cover untested scenarios like chain reorganization,” Quarkslab said.
OSTIF added that while no critical, high, or medium-impact vulnerabilities emerged, the audit provided valuable feedback, insights, and enhancements to the testing systems.
