Bitcoin Core Developers Address High-Severity Bug Affecting Mining Nodes
Bitcoin Core developers have recently revealed a high-severity bug that could prevent certain nodes from building new blocks. This flaw was identified during chain reorganizations and has the potential to corrupt the node’s mempool. Fortunately, a fix was implemented over a year ago, but older nodes remain at risk.
Details of the Bug
On November 10, 2026, Bitcoin Core published an advisory regarding CVE-2025-62861, which affects versions 28.0 to 28.2 and 29.0 to 29.1. The root cause of the issue lies in a rule called sibling eviction, which malfunctioned during chain reorganizations. This glitch allowed nodes to drop restored transactions while retaining their descendants, leading to inconsistencies in the mempool.
A block template, essential for miners to create new blocks, was rendered invalid due to this bug. The only remedy for affected nodes was to restart them, prompting a rebuild of the mempool from scratch.
Who Is Affected?
The primary parties at risk are miners and pool operators running the vulnerable versions. Once the mempool became inconsistent, the affected nodes could no longer produce valid block templates. The flaw was responsibly reported by security researcher Niklas Goegge on September 26, 2025, with a fix submitted shortly thereafter by developer Greg Sanders.
In addition to the high-severity bug, Bitcoin Core disclosed two other vulnerabilities in the same advisory. One could stall block processing, while another improperly granted permissions to inbound Tor connections. Operators still using versions 28.0 through 29.1 are urged to upgrade immediately to avoid potential issues.
Updated 17:31 UTC
New Facts on Bitcoin Core Developers and Mining Nodes
On November 10, it was disclosed that thousands of Bitcoin nodes had granted anonymous users access that bypassed security limits. This issue was traced back to misplaced peer privileges related to bundled Tor-and-whitelist settings.
Fixes for this vulnerability have been available since October 2025.
FAQ
What is the high-severity bug identified by Bitcoin Core developers?
The high-severity bug, identified as CVE-2025-62861, affects Bitcoin Core versions 28.0 to 28.2 and 29.0 to 29.1. It can prevent certain nodes from building new blocks during chain reorganizations, leading to inconsistencies in the mempool.
How does the bug affect mining nodes?
The bug causes affected nodes to drop restored transactions while retaining their descendants, resulting in an invalid block template for miners. This inconsistency prevents the nodes from producing valid blocks.
What should operators do if they are using vulnerable versions?
Operators using Bitcoin Core versions 28.0 through 29.1 are urged to upgrade immediately to avoid potential issues related to the bug and to ensure their nodes can build new blocks effectively.
When was the bug reported and fixed?
The bug was responsibly reported by security researcher Niklas Goegge on September 26, 2025, and a fix was submitted shortly thereafter by developer Greg Sanders. However, older nodes that have not been updated remain at risk.
Are there any other vulnerabilities disclosed in the advisory?
Yes, in addition to the high-severity bug, Bitcoin Core disclosed two other vulnerabilities: one that could stall block processing and another that improperly granted permissions to inbound Tor connections.
Comments
Comments are moderated before publish.
No comments yet — be the first.