Spring Cloud Gateway 4.3.1 does not support Kotlin 1.9

[neptoon]

Describe the bug
Upgrading from 4.3.0 to 4.3.1 (due to CVE-2025-41243), I noticed that projects do not compile anymore if they use Kotlin 1.9, which is the default Kotlin version used by Spring Boot 3.x. Is breaking compatibility intended for a patch release?

Sample
See the attached sample pom.xml files.

pom-4.3.0.xml uses the default version of spring-cloud-gateway-server from Spring Cloud 2025.0.0 and compiles fine with mvn clean compile.

pom-4.3.1.xml upgrades spring-cloud-gateway-server to 4.3.1 and compiling the project results in the following error message:

/home/user/.m2/repository/org/springframework/cloud/spring-cloud-gateway-server/4.3.1/spring-cloud-gateway-server-4.3.1.jar!/META-INF/spring-cloud-gateway-server.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 2.2.0, expected version is 1.9.0.

[neptoon]

The pom.xml of spring-cloud-gateway-server 4.3.1 does also contain an (optional) dependency on Kotlin version 1.9 (not 2.2):

https://repo1.maven.org/maven2/org/springframework/cloud/spring-cloud-gateway-server/4.3.1/spring-cloud-gateway-server-4.3.1.pom