Bitcoin Core reveals flaws affecting mining and Tor
📋 Summary
Bitcoin Core disclosed three vulnerabilities fixed since October 2025, including a high-severity flaw capable of interrupting block creation by mining nodes. Two other issues affected block processing and connection permissions via Tor. Operators using current versions are already protected.
Bitcoin Core made public three security issues that had been fixed in October 2025. The most serious could leave a mining node unable to assemble valid blocks after a blockchain reorganization, requiring the software to be restarted to resume operation.
The flaws were detailed on November 10, after support for the last vulnerable release line ended. There are no public reports of exploitation, loss of funds, or violations of Bitcoin’s consensus rules. Even so, the disclosure is relevant to miners and node operators running older versions of the client.
High-severity flaw affected mining nodes
The most serious vulnerability, identified as CVE-2025-62861, affected Bitcoin Core versions 28.0 to 28.2 and 29.0 to 29.1. The issue occurred in a specific situation: when a blockchain reorganization returned transactions from discarded blocks to the mempool, the queue of unconfirmed transactions.
During this process, a rule applied to TRUC transactions, also known as version 3 transactions, could remove one transaction while leaving other transactions that depended on it in the mempool. This resulted in an inconsistent state. For a miner, this meant that the block template produced by the node failed its own validity check.
The affected node returned to normal after being restarted, because the mempool was reloaded consistently. The fix now prevents the “sibling eviction” rule from being applied when transactions are reinserted after a reorganization.
📋 Summary
Bitcoin Core disclosed three vulnerabilities fixed since October 2025, including a high-severity flaw capable of interrupting block creation by mining nodes. Two other issues affected block processing and connection permissions via Tor. Operators using current versions are already protected.
Bitcoin Core made public three security issues that had been fixed in October 2025. The most serious could leave a mining node unable to assemble valid blocks after a blockchain reorganization, requiring the software to be restarted to resume operation.
The flaws were detailed on November 10, after support for the last vulnerable release line ended. There are no public reports of exploitation, loss of funds, or violations of Bitcoin’s consensus rules. Even so, the disclosure is relevant to miners and node operators running older versions of the client.
High-severity flaw affected mining nodes
The most serious vulnerability, identified as CVE-2025-62861, affected Bitcoin Core versions 28.0 to 28.2 and 29.0 to 29.1. The issue occurred in a specific situation: when a blockchain reorganization returned transactions from discarded blocks to the mempool, the queue of unconfirmed transactions.
During this process, a rule applied to TRUC transactions, also known as version 3 transactions, could remove one transaction while leaving other transactions that depended on it in the mempool. This resulted in an inconsistent state. For a miner, this meant that the block template produced by the node failed its own validity check.
The affected node returned to normal after being restarted, because the mempool was reloaded consistently. The fix now prevents the “sibling eviction” rule from being applied when transactions are reinserted after a reorganization.