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Expand Up @@ -7,6 +7,8 @@ tags:
- CRS-News
- Migration
- CRS-v4
images:
- /images/2026/04/pexels-toulouse-18332033.jpg
title: 'Migrating from CRS 3.3 to CRS 4.25 LTS — Part 1: Overview'
slug: 'migrating-crs-3-to-4-part-1-overview'
---
Expand All @@ -15,6 +17,8 @@ The release of [CRS v4.25.0 LTS]({{< ref "blog/2026-03-28-announcing-crs-v4-25-l

This is the first post in a series walking through everything you need to know to migrate from CRS 3.3.9 (the last CRS 3 LTS release) to CRS 4.25.0 LTS. The series is not a quick upgrade guide. It is a deliberate, post-by-post treatment of each dimension of the migration so that you can plan and execute without surprises.

{{< figure src="/images/2026/04/pexels-toulouse-18332033.jpg" >}}*© Maël BALLAND (pexels.com)*

## Why Migrate?

CRS 3.3.x is in security-only maintenance. It receives backports for confirmed security vulnerabilities but nothing else: no false positive fixes, no new detections, no engine compatibility improvements. Every month you stay on CRS 3.3.x, the gap between your deployment and the state of the art widens.
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