Bitcoin Core developers have disclosed three security vulnerabilities that could significantly impact the network’s functionality. One of these vulnerabilities, marked as highly critical, posed a risk of inhibiting Bitcoin miners from generating new blocks under specific conditions. Bitcoin Core is the fundamental client software used by numerous nodes across the Bitcoin network.
Details of Vulnerabilities and Affected Versions
According to security announcements released on November 10, the most severe vulnerability is cataloged under CVE-2025-62861. This flaw could result in inconsistencies in a node’s mempool status if a blockchain reorganization occurs. The mempool serves as a temporary holding area for unconfirmed transactions awaiting block inclusion.
This vulnerability impacted versions 28.0 through 28.2 and versions 29.0 and 29.1 of Bitcoin Core. Security researcher Niklas Goegge reported the issue on September 26, 2025.
Bitcoin Core developers stated that the CVE-2025-62861 flaw could disrupt the mining process by corrupting the mempool status after blockchain reorganizations.
Additional Medium Severity Flaws Revealed
Developers also disclosed two medium severity vulnerabilities. The first, coded as CVE-2025-62859, allowed malicious network participants to exploit changes in transaction witness data to slow block processing. Under certain circumstances, an affected node could be forced to wait up to ten minutes before processing a block.
This exploit could repeatedly be executed on nodes operating under specific configurations. Security researcher Eugene Siegel detected this vulnerability in April 2025.
The other vulnerability, CVE-2025-62860, involved Bitcoin nodes operating through the Tor network. Developers noted that thousands of nodes on the Bitcoin main network allowed incoming Tor connections. However, nodes that utilized an optional whitelist configuration were not affected.
Developers reported that one medium severity flaw extended block processing time, while another affected nodes with certain Tor configurations.
Fixes Released in October
The disclosed security issues are not newly discovered. The Bitcoin Core team addressed all of these vulnerabilities in October 2025. Fixes were included in the Bitcoin Core 30.0 release on October 10 and the subsequent 29.2 update on October 14.
The critical mining vulnerability was also rectified in the Bitcoin Core 28.3 version, providing a path for node operators using older affected versions to update their software.
