Bitcoin Core 32.0 enters final testing with fee, speed and security changes
Bitcoin Core, the main software used to run Bitcoin nodes, has moved its next major update into its final testing stage. The first release candidate for version 32.0 was tagged on September 14, with developers aiming to release the finished version on October 10, according to the project's release schedule.
Bitcoin Core lets a computer independently check transactions and blocks against Bitcoin's rules, rather than relying on another service. A node is a computer that runs this software and helps keep the network running. Version 32 does not change those underlying rules, but it does change how the software estimates fees, processes blocks, and handles certain wallet features.
What the release candidate includes
- A new fee estimator that looks at transactions currently waiting to be confirmed, working alongside the existing one that studies fees in past blocks.
- The ability for nodes to fetch transaction data from their databases using several processing threads at once, with eight threads set as the standard.
- A switch to PSBT version 2 as the default format for four commands that create partially signed transactions, which are files passed between wallet software and signing devices before bitcoin is sent.
- A fix for a vulnerability that had existed since Bitcoin Core 24.0 on non-Windows systems.
- A replacement of Bitcoin Core's existing web server, which handles requests from other applications.
How the new fee estimator works
Today, Bitcoin Core estimates how much a user should pay for a transaction mostly by looking at the fees attached to transactions that made it into previous blocks. Version 32 adds a second estimator that looks at transactions waiting to be confirmed in the memory pool, the holding space for unconfirmed transactions.
The software will compare the two numbers and can recommend the lower fee when current network conditions allow. The change is designed so that recommended fees fall more quickly once congestion clears, instead of continuing to reflect more expensive transactions from earlier blocks, according to the draft release notes.
Faster block checks on catching-up nodes
Nodes can now fetch transaction data from their databases using several processing threads at the same time while checking blocks. A thread is a separate lane of work a computer can run in parallel. Bitcoin Core 32 will use eight of those threads by default, which is meant to cut the time a node spends waiting for information stored on its hard drive while it is catching up with the blockchain. The blockchain is the shared ledger that records every Bitcoin transaction.
The security flaw being patched
Developers fixed a flaw that had been present in the software since Bitcoin Core 24.0 on non-Windows systems. An authenticated user with permission to create wallets could give one a specially crafted name and, under certain conditions, cause commands to run on the computer hosting the node. The attack required the operator to have turned on a feature called walletnotify, which automatically runs a chosen command when a wallet transaction occurs. Bitcoin Core 32 now treats wallet names as literal text, rather than allowing parts of the name to be interpreted as commands.
Wallet and web server changes
Four Bitcoin Core commands used to create partially signed bitcoin transactions will start using the newer PSBT version 2 format by default. Applications can still ask for the older format, but services built directly around those Core commands will need to make sure they support version 2.
Version 32 also replaces Bitcoin Core's existing web server, which handles requests from other applications communicating with the node. Developers also fixed a memory-exhaustion flaw in the new web server before the software's stable release.
What is confirmed
- The first release candidate for Bitcoin Core 32.0 was tagged on September 14.
- Developers are aiming for a finished release on October 10, based on the project's release schedule.
- The update changes fee estimation, block processing, wallet behavior, and the web server.
- The update does not change Bitcoin's consensus rules.
Why this matters
Bitcoin Core is the software most operators use to run a Bitcoin node, so changes to it can affect anyone running the network themselves or relying on tools built around its features. The new fee estimator could help users pay less when the network is quiet, while the threading change is aimed at making it faster for nodes to catch up after being offline. The security fix closes a route that could have let a logged-in user with the right permissions run commands on the host machine.