Bitcoin Core 32.0 moves into release-candidate testing
The next major version of Bitcoin Core has entered its final testing phase, bringing a collection of changes focused on transaction fee estimation, node performance, wallet functionality and security.
Bitcoin Core is the software that allows users to operate Bitcoin nodes and independently verify transactions and blocks against the network's rules. The upcoming 32.0 release does not change Bitcoin's consensus rules, but it introduces several changes to how the software handles transactions and communicates with other applications.
According to the official Bitcoin Core 32.0 release schedule, the project entered the release-candidate cycle on September 14, 2026, when developers split the 32.x branch from the main development branch and tagged v32.0rc1. The current schedule targets the final v32.0 release for October 10, 2026.
The move into release-candidate testing means the focus has shifted away from adding major features and toward identifying and fixing remaining bugs before the stable version is published.
New approach to Bitcoin transaction fee estimation
One of the user-facing changes in Bitcoin Core 32.0 concerns how the software estimates the fee required for a transaction.
Bitcoin Core traditionally bases its fee estimates largely on historical transaction data, particularly transactions that were confirmed in previous blocks. Version 32.0 adds another estimator that examines transactions currently waiting in the mempool, giving the software a more immediate view of network conditions.
The two estimates can then be compared, allowing the software to select a lower fee when current conditions support it. The goal is to make fee recommendations respond more quickly when network congestion declines instead of continuing to reflect higher fees from earlier periods.
This builds on Bitcoin Core's longer-term work on fee estimation. Previous releases have also changed the default estimation behavior and fee-tracking ranges as developers have refined how the software responds to changing transaction demand.
For ordinary users, the practical effect is that wallets using Bitcoin Core's fee estimation could potentially adjust their recommended transaction fees more quickly when the mempool becomes less crowded.
Block processing gets more parallel
Bitcoin Core 32.0 also includes a performance improvement for nodes that are processing blocks.
Nodes can retrieve transaction-related data from their databases using multiple processing threads while validating blocks. The new configuration uses eight threads by default, reducing the amount of time a node can spend waiting for information to be retrieved from disk during blockchain processing.
This is particularly relevant when a node is catching up with the Bitcoin blockchain. During that process, the software must download and validate large numbers of blocks, repeatedly accessing data stored on disk.
The change does not alter Bitcoin's validation rules. Instead, it is intended to make the underlying software more efficient when performing the same validation work.
Wallet security fix addresses command-execution flaw
Security is another important part of the Bitcoin Core 32.0 update.
Developers fixed a vulnerability affecting non-Windows systems in which an authenticated RPC user with permission to create wallets could potentially execute commands on the machine running the Bitcoin node. The attack required the node operator to have enabled the walletnotify feature, which can automatically run a configured command when a wallet transaction is detected.
The problem involved specially crafted wallet names. Under certain conditions, parts of a wallet name could be interpreted as command-related syntax rather than being handled strictly as text. The fix changes the handling so wallet names are treated literally. The vulnerability was fixed in development before Bitcoin Core 32.0's stable release.
The issue required several conditions to be present, including authenticated RPC access, permission to create wallets and an enabled walletnotify configuration. It was therefore not an attack that could simply be launched remotely against an ordinary Bitcoin node through the peer-to-peer network.
For node operators, however, the fix is significant because a Bitcoin Core node can hold wallet data and operate with the permissions of the account running the software.
New HTTP server receives a memory-exhaustion fix
Bitcoin Core 32.0 also addresses a separate issue involving its new HTTP server.
During an audit using the Kimi K3 AI model, developers identified a scenario in which the server could continue reading incoming data from a client while it was already processing an earlier request. Under certain conditions, this could allow incoming data to accumulate in memory faster than the server could process it.
The resulting memory-exhaustion scenario was addressed in Bitcoin Core pull request #36123. The change prevents the server from continuing to read from a connection while it is busy processing a request, allowing normal TCP backpressure to limit the amount of incoming data that can accumulate.
The testing described in the original report showed how severe the memory growth could become under the affected conditions. In one test, 16 unauthenticated REST connections increased memory usage from about 46 MB to roughly 3 GB in around one minute. After the fix, a 90-second test used approximately 3 MB, compared with 3.2 GB before the change.
The vulnerability was identified before the new HTTP server appeared in a stable Bitcoin Core release, allowing developers to address it during development rather than after deployment.
PSBT version 2 becomes the default for several commands
Bitcoin Core 32.0 also changes how four wallet commands create Partially Signed Bitcoin Transactions, commonly known as PSBTs.
PSBTs allow a transaction to move between different pieces of wallet software or signing devices before it is finalized and broadcast. They are particularly useful for workflows involving hardware wallets, multisignature setups and offline signing.
In version 32.0, four Bitcoin Core commands used to create these transactions will use PSBT version 2 by default. Applications can still request the older format, but developers integrating directly with these Core commands will need to ensure their software handles the newer default.
The change is part of Bitcoin Core's continuing modernization of wallet and transaction infrastructure rather than a change to how Bitcoin transactions are ultimately validated by the network.
What Bitcoin Core 32.0 means for node operators
Bitcoin Core 32.0 combines several improvements rather than introducing a single consensus-level change.
For users running nodes, the update brings faster database access during block processing, revised fee-estimation behavior and multiple security fixes. Wallet developers also need to account for the new PSBT default, while applications interacting with the node's HTTP interfaces should benefit from the server-side memory protections.
The official Bitcoin Core repository remains the primary source for the software, development changes and release information.
The project is currently targeting October 10, 2026 for the final 32.0 release, following the release-candidate testing period that began September 14.
Because version 32.0 is still in the release-candidate stage, the final contents or timing could change if additional issues are discovered during testing. For now, the update represents a broad maintenance and performance release focused on making Bitcoin Core more efficient, secure and responsive without changing Bitcoin's underlying consensus rules.
