diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5fd009f811..61f63362d8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,30 @@
 
 All notable changes to this project will be documented in this file.
 
+## [4.2.21] - 2025-05-06
+
+### Security
+
+- Update dependencies
+
+### Added
+
+- Add warning for REDIS_NAMESPACE deprecation at startup (#34581 by @ClearlyClaire)
+- Add built-in context for interaction policies (#34574 by @ClearlyClaire)
+
+### Changed
+
+- Change activity distribution error handling to skip retrying for deleted accounts (#33617 by @ClearlyClaire)
+
+### Removed
+
+- Remove double-query for signed query strings (#34610 by @ClearlyClaire)
+
+### Fixed
+
+- Fix incorrect redirect in response to unauthenticated API requests in limited federation mode (#34549 by @ClearlyClaire)
+- Fix sign-up e-mail confirmation page reloading on error or redirect (#34548 by @ClearlyClaire)
+
 ## [4.2.20] - 2025-04-02
 
 ### Add
diff --git a/docker-compose.yml b/docker-compose.yml
index 84ec231d5e..424f6822aa 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -56,7 +56,7 @@ services:
 
   web:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.2.20
+    image: ghcr.io/mastodon/mastodon:v4.2.21
     restart: always
     env_file: .env.production
     command: bash -c "rm -f /mastodon/tmp/pids/server.pid; bundle exec rails s -p 3000"
@@ -77,7 +77,7 @@ services:
 
   streaming:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.2.20
+    image: ghcr.io/mastodon/mastodon:v4.2.21
     restart: always
     env_file: .env.production
     command: node ./streaming
@@ -95,7 +95,7 @@ services:
 
   sidekiq:
     build: .
-    image: ghcr.io/mastodon/mastodon:v4.2.20
+    image: ghcr.io/mastodon/mastodon:v4.2.21
     restart: always
     env_file: .env.production
     command: bundle exec sidekiq
diff --git a/lib/mastodon/version.rb b/lib/mastodon/version.rb
index 97a92ef743..6223a7595a 100644
--- a/lib/mastodon/version.rb
+++ b/lib/mastodon/version.rb
@@ -13,7 +13,7 @@ module Mastodon
     end
 
     def patch
-      20
+      21
     end
 
     def default_prerelease