Bitcoin Core Discloses Three Patched Flaws, Including High-Severity Mining Bug

Bitcoin Core has publicly disclosed three previously patched security vulnerabilities, including a high-severity flaw affecting block-template creation. The disclosures were published on November 10, 2026.

The high-severity issue, tracked as CVE-2025-62861, could leave a node unable to create valid block templates following a chain reorganization. According to Bitcoin Core’s disclosure, recovery required restarting the affected node.

The other two issues were classified as medium severity. They involved compact-block processing and the handling of whitelist permissions for inbound Tor connections.

Fixes for all three vulnerabilities had already been released before the public disclosures. The fixes shipped across Bitcoin Core versions 28.3, 29.2, and 30.0.

Reorganization flaw could halt block-template creation

CVE-2025-62861 concerned TRUC sibling eviction during a chain reorganization. Bitcoin Core said the condition could leave the mempool in an inconsistent state.

In that state, a node could be prevented from producing valid block templates until it was restarted. Block templates are particularly relevant to mining operations because they are used to assemble candidate blocks.

The disclosure classifies CVE-2025-62861 as high severity. The issue was patched before its details were made public.

Two medium-severity issues affected peers and block processing

Bitcoin Core also disclosed CVE-2025-62859, a medium-severity issue involving witness malleation in compact blocks. A malicious peer could use the condition to stall block processing.

CVE-2025-62860 was another medium-severity issue. It could cause incoming Tor peers to receive whitelist permissions when a matching non-default IP range was configured.

The disclosures underline that node behavior can be affected by both peer-to-peer message handling and configuration-specific permission logic. Bitcoin Core said fixes for these issues were released before disclosure.

• CVE-2025-62859: block-processing stall through witness malleation in compact blocks.
• CVE-2025-62860: incorrect whitelist permissions for certain inbound Tor connections.
• CVE-2025-62861: block-template creation could remain unavailable after a reorganization until restart.

What the disclosures mean for operators

The public notices describe patched vulnerabilities rather than newly released fixes. Operators can use the affected versions and issue descriptions to assess their own upgrade status and configurations.

For mining-related infrastructure, the high-severity issue is notable because its stated effect was the inability to create valid block templates after a reorganization. The other two issues concerned block-processing availability and peer permissions.

The disclosures arrive as operational issues remain central to the mining sector, including developments involving pool activity and infrastructure deployment. Readers can also review coverage of Binance Pool’s final week of activity before its announced shutdown and SunBit’s reported mining-heating deployments in Finland.

Continue reading: Binance Pool’s final week of activity before its announced shutdown on BTCNews.

Continue reading: SunBit’s reported mining-heating deployments in Finland on BTCNews.

Sources

• Bitcoin Core: CVE-2025-62861 – Block template creation halted by TRUC sibling eviction during reorg
• Bitcoin Core: CVE-2025-62859 – Block processing stall via witness malleation
• Bitcoin Core: CVE-2025-62860 – Inbound Tor connections wrongly receive -whitelist permissions
• The Block: Bitcoin Core discloses three patched security flaws, including high-severity mining bug

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