# Release: AWS IoT Greengrass Core v2.5.2 software update on December 3, 2021
<a name="greengrass-release-2021-12-03"></a>

This release provides version 2.5.2 of the Greengrass nucleus component.

**Release date:** December 3, 2021

**Topics**
+ [Public component updates](#greengrass-2021-12-03-components)

## Public component updates
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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 2.5.2 of the [Greengrass nucleus](greengrass-nucleus-component.md) is available.<a name="changelog-nucleus-2.5.2"></a>**Bug fixes and improvements**<br />   Fixes an issue where after the Greengrass nucleus updates, the Windows service fails to start again after you stop it or reboot the device.    | 
| AWS IoT Device Defender | Version 3.0.1 of the [AWS IoT Device Defender](device-defender-component.md) component is available.<br /><a name="changelog-device-defender-3.0.0-major-version-changes"></a>This version of the AWS IoT Device Defender component expects different configuration parameters than version 2.x. If you use a non-default configuration for version 2.x, and you want to upgrade from v2.x to v3.x, you must update the component's configuration. For more information, see [AWS IoT Device Defender component configuration](device-defender-component.md#device-defender-component-configuration).<a name="changelog-device-defender-3.0.1"></a>**New features**<br />   Adds support for core devices that run Windows.   Changes the component type from Lambda component to generic component. This component now no longer depends on the legacy subscription router component to create subscriptions.    Adds the new `UseInstaller` configuration parameter that lets you optionally disable the installation script that installs component dependencies.    |