- Bitcoin Core disclosed three patched flaws tied to denial-of-service and privacy risks.
- The most serious issue could stop block template creation until an affected node was restarted.
- Developers said none of the bugs were critical and reported no known exploitation.
Bitcoin Core developers disclosed three patched vulnerabilities in software used by most Bitcoin nodes, including a high-severity Bitcoin Core bug that could interfere with mining activity. The most serious issue affected block template creation, the process miners use to assemble new blocks. In the advisory, developers said a chain reorganization could incorrectly evict some transactions and corrupt a node’s mempool, leaving that node unable to build block templates until it was restarted. The flaws were described as denial-of-service and privacy issues rather than problems that could enable coin theft, coin forgery, or a broader protocol failure.
Bitcoin Core bug affected mining workflow
The most serious Bitcoin Core bug was identified as CVE-2025-62861. According to the advisory, it involved block template creation, which is central to how miners prepare candidate blocks. During a chain reorganization, certain transactions could be removed in error, damaging the state of the mempool where unconfirmed transactions are held.
If that happened, the affected node could no longer create block templates until it was restarted. For a miner, that would interrupt the work tied to earning block rewards. Bitcoin Core classified the issue as high severity, but it did not place it in the project’s top critical category.
Other Bitcoin Core bug fixes disclosed
A second issue, CVE-2025-62859, could let a peer stall a node’s block processing. Bitcoin Core said this could happen if a compact block was announced with a manipulated witness, which the advisory described as a form of transaction malleation.
The third flaw, CVE-2025-62860, involved inbound connections over the Tor network. Those connections were incorrectly granted whitelist permissions, which removed some denial-of-service and privacy protections that would normally apply to affected nodes.
Bitcoin Core bug severity and disclosure details
Bitcoin Core said all three vulnerabilities had been patched and that none rose to the critical level. The project reserves that category for more severe cases such as protocol-level coin theft, unauthorized coin creation, or a permanent network-wide chain split.
Developers also said they had no evidence that the flaws were exploited. The software fixes were released earlier, with the public advisories following later under Bitcoin Core’s disclosure process. Node operators are generally encouraged to run the latest version to stay protected from a disclosed Bitcoin Core bug.
Security policy changed as AI finds bugs faster
The disclosures came as Bitcoin Core has been changing how it handles some security issues. The project recently updated its policy to account for vulnerabilities that can be found easily with AI, creating a category for flaws that can be surfaced through a simple prompt.
Under that updated approach, Bitcoin Core now patches and discloses those easily discoverable issues immediately instead of keeping them under a longer embargo. The policy shift reflects concern that large language models have made some weaknesses faster to uncover, while the volunteer Bitcoin Red Team has been trying to find such flaws before attackers do.
Conclusion
The latest Bitcoin Core bug disclosures covered three patched vulnerabilities in software that powers most of the Bitcoin network’s nodes. The most serious Bitcoin Core bug could disrupt mining by corrupting a node’s mempool during a chain reorganization and stopping block template creation until restart. Two other issues affected block processing and Tor connection protections. Bitcoin Core said none of the flaws were critical and reported no signs of real-world exploitation. The disclosures also arrived as the project updates its security policy to reflect how AI can make some vulnerabilities easier and faster to discover.
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