Spring Boot 4.0.9, 4.1.2 and 4.2.0-RC1 releases published

Around 02:04 Korean time on 2026-10-23, official GitHub releases published stable 4.0.9 and 4.1.2 and prerelease 4.2.0-RC1. Official blog posts dated the same day confirm Maven Central availability, with 99 fixes, documentation and dependency changes in 4.0.9, 126 in 4.1.2, and 113 enhancements, documentation and dependency changes and fixes in RC1. 4.0.9 includes fixes for JWT rejection with empty issuer-uri and jwk-set-uri values, nested JAR contention and manifest handling, and shutdown hangs. RC1 includes nested JAR reading and class/resource lookup optimizations, an Ubuntu 26.04-based default Buildpacks builder, and spring-boot-properties-migrator support for failing startup on errors or warnings. Developers should distinguish stable releases from the RC and check changes relevant to their version line.