> ## Documentation Index
> Fetch the complete documentation index at: https://doc.lucidworks.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Fusion 4.2.6 SP2 Release Notes

[localhost link]: http://localhost:3000/docs/4/fusion-server/release-notes/4.2.6-sp2-release-notes

[mintlify link]: https://doc.lucidworks.com/docs/4/fusion-server/release-notes/4.2.6-sp2-release-notes

[old doc.lw link]: https://doc.lucidworks.com/fusion-server/4.2/i552i1

**Release date:** 20 April 2022

**Component versions:**

|                                     |                  |             |                        |              |              |
| ----------------------------------- | ---------------- | ----------- | ---------------------- | ------------ | ------------ |
| Solr 7.7.3  See Solr updates below. | ZooKeeper 3.4.13 | Spark 2.3.2 | Jetty 9.4.35.v20201120 | Ignite 2.6.0 | Log4j 2.17.1 |

**More information about support dates can be found at [Lucidworks Fusion Product Lifecycle](/docs/policies/lifecycle-policies/lw-fusion-product-lifecycle).**

<Tip>
  **Looking for download links?**

  Check out the [Fusion 4.2.6 Service Pack application files](/docs/4/fusion-server/reference/fusion-server-4-x-file-download-links#fusion-4-2-6-service-pack-application-files).
</Tip>

## Improvements

### Solr

The following fixes have been applied to solr:

* SOLR-13336
* SOLR-14073
* SOLR-14058

### Log4j

<Tip>
  **Important**

  Main Fusion services upgraded to use Log4j 2.17.2 library.
</Tip>

* Solr upgraded to use Log4j 2.17.1.
* App Insights and App Studio upgraded to use Log4j 2.17.1 library.
* Removed Log4j1x.jars from various services.

## Other changes

* Removed Build UI feature due to outdated components.