# Ruby: what changed from 3 to 4

- Product: Ruby (https://whatsnew.fyi/product/ruby)
- Vendor: Ruby
- Range: changelog entries numbered after 3.4.10 up to and including 4.0.6, stable releases only
- Entries below: 4 releases (newest first)
- Resolved: 3 is 3.4.10 and 4 is 4.0.6, the newest stable release of each major we track
- Carrying security changes: 2 · CVEs mentioned: 2 · Mentioning breaking changes: 0 · Removing or deprecating something: 0
- Page: https://whatsnew.fyi/product/ruby/compare/3...4

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

## What changed (3 changes, grouped by kind)

### Fixed

#### 4.0.5 (2026-05-20)

- Fix build system regression from Ruby 4.0.4

### Security

#### 4.0.5 (2026-05-20)

- Fix use-after-free in pthread-based getaddrinfo timeout handler (CVE-2026-46727)

#### 4.0.3 (2026-04-21)

- Fix CVE-2026-41316 in ERB 6.0.1.1

_2 releases carry no categorized changes yet: 4.0.6, 4.0.4._

## Release notes

### 4.0.6 — Ruby 4.0.6 Released

- Date: 2026-07-14
- Version: 4.0.6
- Original notes: https://www.ruby-lang.org/en/news/2026/07/14/ruby-4-0-6-released/
- Permalink: https://whatsnew.fyi/product/ruby/releases/4.0.6

Ruby 4.0.6 has been released. This is a routine update that includes bugfixes. Please see the GitHub releases for further details. Release Schedule We intend to release the latest stable Ruby version…

### 4.0.5 — Ruby 4.0.5 Released

- Date: 2026-05-20
- Version: 4.0.5
- Original notes: https://www.ruby-lang.org/en/news/2026/05/20/ruby-4-0-5-released/
- Permalink: https://whatsnew.fyi/product/ruby/releases/4.0.5

Ruby 4.0.5 has been released. This release only contains a security fix for CVE-2026-46727: Use-after-free in pthread-based getaddrinfo timeout handler and a build system regression in Ruby 4.0.4 unde…

- **security** — Fix use-after-free in pthread-based getaddrinfo timeout handler (CVE-2026-46727)
- **fixed** — Fix build system regression from Ruby 4.0.4

### 4.0.4 — Ruby 4.0.4 Released

- Date: 2026-05-11
- Version: 4.0.4
- Original notes: https://www.ruby-lang.org/en/news/2026/05/11/ruby-4-0-4-released/
- Permalink: https://whatsnew.fyi/product/ruby/releases/4.0.4

Ruby 4.0.4 has been released. This is a routine update that includes bugfixes. Please see the GitHub Releases for further details. Release Schedule We intend to release the latest stable Ruby version…

### 4.0.3 — Ruby 4.0.3 Released

- Date: 2026-04-21
- Version: 4.0.3
- Original notes: https://www.ruby-lang.org/en/news/2026/04/21/ruby-4-0-3-released/
- Permalink: https://whatsnew.fyi/product/ruby/releases/4.0.3

Ruby 4.0.3 has been released. This release only contains ERB 6.0.1.1, which fixes CVE-2026-41316 . If your application calls Marshal.load on untrusted data AND has both erb and activesupport loaded, p…

- **security** — Fix CVE-2026-41316 in ERB 6.0.1.1