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+---
+title: "2.23.1 release notes"
+weight: 955
+toc: true
+f5content-type: reference
+f5product: F5 NGINX Instance Manager
+description: "Release notes for F5 NGINX Instance Manager, including new features, improvements, and bug fixes in each release."
+f5-summary: >
+   Stay up to date with the latest features, improvements, and bug fixes in F5 NGINX Instance Manager. This document provides details about new features, known issues, and resolved problems for each version.
+---
+
+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}
+
+{{< call-out "important" >}}
+For the protection of our customers, NGINX doesn’t disclose security issues until an investigation has occurred and a fix is available.
+{{< /call-out >}}
+
+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]({{< ref "/nim/releases/known-issues.md" >}}) topic.