# 2.23.1 release notes

> Release notes for F5 NGINX Instance Manager, including new features, improvements, and bug fixes in each release.

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September 16, 2026

NGINX Instance Manager 2.23.1 release notes

### Upgrade Paths {#2-23-1-upgrade-paths}

NGINX Instance Manager 2.23.1 supports upgrades from these previous versions:

- 2.20.0 - 2.23.0

If your NGINX Instance Manager version is older, you may need to upgrade to an intermediate version before upgrading to the target version.

### Security updates{#2-23-1-security-updates}

**important:** 
For the protection of our customers, NGINX doesn’t disclose security issues until an investigation has occurred and a fix is available.

This release includes the following security updates:

- [icon: resolved] **Instance Manager vulnerability CVE-2026-90439**<a name="2-23-1-security-updates-Instance-Manager-vulnerability-CVE-2026-90439-47816"></a>

   NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_v3_module module ( [CVE-2026-90439](https://my.f5.com/manage/s/article/K000162604)).

    This issue has been classified as [CWE-122: Heap-based Buffer Overflow](https://cwe.mitre.org/data/definitions/122.html).

### Known issues {#2-23-1-known-issues}

You can find information about known issues in the [Known Issues](/nim/releases/known-issues.md) topic.