A High-Severity Bug Could Have Stalled Bitcoin Mining—Bitcoin Core Has a Fix

In brief

• Bitcoin Core disclosed three now-patched security flaws in the software running most of the network’s nodes, covering denial-of-service and privacy issues rather than anything enabling coin theft or forgery.
• The most serious could corrupt a node’s mempool during a chain reorganization, halting a miner’s ability to create block templates until restarted.
• None reached Bitcoin Core’s “critical” tier, and no exploitation was reported.

Bitcoin Core developers have disclosed three security vulnerabilities in the software that runs most of the Bitcoin network, including one high-severity bug that could disrupt mining, all of which have since been fixed.

The flaws, detailed in a batch of security advisories, span denial-of-service and privacy issues rather than anything that would let an attacker steal coins or forge Bitcoin.

Bitcoin Core, the reference software operating the majority of the network’s nodes, classifies vulnerabilities into four tiers, from “low” to “critical,” and these fell into the middle of that range.

The most serious, tracked as CVE-2025-62861, concerns block template creation, the process miners rely on to assemble new blocks.

According to the advisory, a chain reorganization could trigger an erroneous eviction of certain transactions, corrupting a node’s mempool, its waiting room for unconfirmed transactions, so that an affected node could no longer build block templates until it was restarted. For a miner, that means a halt to the very work that earns block rewards.