# Release: AWS IoT Greengrass Core v2.5.1 software update on November 23, 2021
<a name="greengrass-release-2021-11-23"></a>

This release provides version 2.5.1 of the Greengrass nucleus component.

**Release date:** November 23, 2021

**Topics**
+ [Public component updates](#greengrass-2021-11-23-components)

## Public component updates
<a name="greengrass-2021-11-23-components"></a>

The following table lists AWS-provided components that include new and updated features.

**Important**  <a name="component-patch-update-note"></a>
<a name="component-patch-update"></a>When you deploy a component, AWS IoT Greengrass installs the latest supported versions of all of that component's dependencies. Because of this, new patch versions of AWS-provided public components might be automatically deployed to your core devices if you add new devices to a thing group, or you update the deployment that targets those devices. Some automatic updates, such as a nucleus update, can cause your devices to restart unexpectedly.   
<a name="component-version-pinning"></a>To prevent unintended updates for a component that is running on your device, we recommend that you directly include your preferred version of that component when you [create a deployment](create-deployments.md). For more information about update behavior for AWS IoT Greengrass Core software, see [Update the AWS IoT Greengrass Core software (OTA)](update-greengrass-core-v2.md).


| **Component** | **Details** | 
| --- | --- | 
| Greengrass nucleus | Version 2.5.1 of the [Greengrass nucleus](greengrass-nucleus-component.md) is available.<a name="changelog-nucleus-2.5.1"></a>**Bug fixes and improvements**<br />   Adds support for 32-bit versions of the Java Runtime Environment (JRE) on Windows.   Changes thing group removal behavior for core devices whose AWS IoT policy doesn't grant the `greengrass:ListThingGroupsForCoreDevice` permission. With this version, the deployment continues, logs a warning, and doesn't remove components when you remove the core device from a thing group. For more information, see [Deploy AWS IoT Greengrass components to devices](manage-deployments.md).   Fixes an issue with system environment variables that the Greengrass nucleus makes available to Greengrass component processes. You can now restart a component for it to use the latest system environment variables.    |