Bitcoin Core, the application utilized to operate Bitcoin nodes, has advanced its upcoming major update into the final testing phase, bringing adjustments to transaction fees, block processing speed, and transaction construction methods within wallets.
The initial release candidate for Bitcoin Core 32.0 was tagged on September 14, kicking off the concluding testing period ahead of the developers’ target to launch the final version on October 10, as outlined in the project’s release schedule.
Bitcoin Core allows an individual computer to autonomously verify transactions and blocks against the rules of Bitcoin instead of depending on an external service. Version 32 leaves those underlying rules completely unchanged.
Presently, Bitcoin Core calculates recommended user transaction fees largely by observing the fees linked to transactions included in preceding blocks. Version 32 introduces a secondary estimator that evaluates transactions currently lingering in the mempool awaiting confirmation.
The system evaluates both metrics and can suggest the lower fee option whenever current network dynamics allow for it. According to the draft release notes, this should enable fee estimates to drop more rapidly when network congestion clears rather than persistently mirroring costlier transactions from earlier blocks.
Nodes can now retrieve transaction data from their databases utilizing multiple processing threads simultaneously during block verification. Bitcoin Core will deploy eight such threads by default, cutting down the duration spent waiting on disk-stored information while a node synchronizes with the blockchain.
Furthermore, developers resolved a security flaw present since Bitcoin Core 24.0 on non-Windows operating systems.
An authenticated user possessing permissions to generate wallets could assign a specially formatted name and, under specific conditions, trigger arbitrary command execution on the host machine running the node. This attack vector necessitated the operator to have activated walletnotify, a feature that automatically launches a designated command upon the occurrence of a wallet transaction. Bitcoin Core 32 processes wallet names strictly as literal text rather than permitting portions of those names to be interpreted as executable commands.
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Wallet Changes And A Memory Flaw
Four Bitcoin Core commands utilized for generating partially signed transactions will likewise transition to employing the newer PSBT version 2 format by default. Such transactions are routinely exchanged between wallet applications and signing hardware prior to dispatching bitcoin.
Software programs can still explicitly request the legacy format, but services engineered directly around those specific Core commands will need to guarantee compatibility with version 2.
Version 32 additionally supersedes Bitcoin Core’s legacy web server, which manages incoming requests from external applications interacting with a node.
An evaluation of the new server, conducted leveraging Moonshot AI’s Kimi K3 model, revealed that it could continuously ingest data from a client while concurrently handling a prior request. Such incoming data accumulated within memory faster than the server could flush it out, establishing a mechanism to steadily escalate a node’s memory consumption until exhaustion occurred.
The developer responsible for the patch characterized the issue as a memory-exhaustion vulnerability. Because this newly introduced server has not yet featured in a stable Bitcoin Core release, the bug was successfully identified prior to the deployment of version 32.
Testing also demonstrated that this vulnerability impacted Bitcoin Core’s REST interface, which operates without requiring authentication credentials.
Sixteen unauthenticated REST connections propelled a test node’s memory utilization from 46 MB to roughly 3 GB in approximately one minute. A 90-second evaluation consumed 3.2 GB of RAM prior to the application of the fix and merely about 3 MB subsequent to it.
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Originally published at https://www.coindesk.com/tech/2026/09/16/bitcoin-core-32-enters-final-testing-with-faster-validation-fee-changes-and-security-fixes.
