Bitcoin Core, the reference implementation of the Bitcoin protocol, has disclosed three previously patched security vulnerabilities, among them a high-severity flaw that could have disrupted Bitcoin mining operations. The advisories, published on November 10, 2026, detail risks to block creation, transaction processing, and network privacy across older versions of the software.

The disclosures appeared more than a year after the fixes themselves, which shipped in October 2025. Because the vulnerabilities affected older Bitcoin Core releases, the delayed announcement raises concerns for miners and node operators still running unpatched software.

High-Severity Bug Threatened Mining Operations

The most serious issue, tracked as CVE-2025-62861, affected Bitcoin Core versions 28.0 through 28.2 and 29.0 through 29.1. The flaw concerned transaction handling during blockchain reorganizations — events in which Bitcoin nodes switch to a competing chain history, commonly known as reorgs.

Under certain conditions, the bug could leave the memory pool, or mempool, in an inconsistent state. Mining nodes affected in this way could fail to generate valid block templates, preventing them from producing new blocks until restarted. Since block templates are the input mining hardware acts on, an affected operator's hashrate would sit idle until the node came back up.

Security researcher Niklas Goegge reported the vulnerability in September 2025. Developers addressed it in Bitcoin Core 30.0, released on October 10, 2025. Details are available in the official disclosure.

Two Medium-Severity Vulnerabilities Exposed Network Risks

Alongside the mining flaw, Bitcoin Core disclosed two medium-severity vulnerabilities involving block processing and Tor network connections.

The first, CVE-2025-62859, allowed malicious peers to delay block processing through manipulated transaction witness data. Attackers could potentially stall processing for up to 10 minutes and repeat the disruption under specific network conditions — a window comparable to the ten-minute block interval Bitcoin's protocol targets.

The second, CVE-2025-62860, affected nodes using certain whitelist configurations in combination with Tor connections. Tor is the anonymity network supported natively in Bitcoin Core, commonly used by node operators to keep their IP addresses private. The flaw could mistakenly grant trusted permissions to incoming Tor peers, weakening protections against denial-of-service attacks and privacy-related risks. Developers acknowledged that thousands of reachable Bitcoin mainnet nodes had configurations that exposed them to the Tor-related issue, though nodes without the affected optional whitelist settings remained unaffected.

Disclosures Underscore Node Maintenance

Bitcoin Core released fixes for all three vulnerabilities in version 30.0, followed by additional patched releases. The final vulnerable release line reached its end of support on October 27, 2026.

The advisories follow earlier security findings concerning memory management and node stability, and they reflect Bitcoin Core's established practice of withholding certain vulnerability details until affected software versions lose support — a common coordinated-disclosure approach that gives users time to upgrade before technical details that could aid attacks on unpatched nodes become public. The November 10 advisories landed roughly two weeks after that end-of-support date, and operators can gauge their exposure by comparing deployed releases against the version ranges named in the disclosures.

Although the latest disclosures concern flaws that have already been corrected, outdated installations may remain exposed. Mining operators and Bitcoin node administrators can reduce these risks by upgrading to supported software versions that contain the security fixes, according to the CryptoMeter io report.