Bitcoin Core bug let any stranger on Tor win trust of nodes

What was the Bitcoin Core Tor bug?

Based on what the project has said, the flaw affected nodes reachable over Tor, the anonymity network that routes traffic through several relays to hide where it comes from. In affected nodes, a peer showing up over Tor was trusted when it should not have been. Further technical details were not available to us, so we are not going to guess at how an attacker might have used it.

A node is simply a computer running Bitcoin software that checks and relays transactions and blocks. Who a node chooses to trust matters, because nodes rely on their peers for information about the network.

A second, more serious bug

The Tor issue was disclosed alongside another flaw rated high severity. This one could stop a miner from producing blocks until someone restarted it. For a mining operation, that means downtime until a person notices and steps in.

Both problems were already fixed before the disclosure, so the practical advice for anyone running a node is the usual one: check which version you run and update if it is older than the patched releases. Anyone running an up-to-date version of Bitcoin Core is not affected by either flaw.