AJP listener fails to start with UT000220 error after updating to JBoss EAP 7.4.25+ / 8.1 update 8+

Issue

• After updating to JBoss EAP 7.4.25+ or 8.1 update 8+, Undertow AJP listeners fail to start with UT000220 errors like below:

ERROR [org.jboss.msc.service.fail] (MSC service thread 1-2) MSC000001: Failed to start service org.wildfly.undertow.listener.ajp: org.jboss.msc.service.StartException in service org.wildfly.undertow.listener.ajp: Failed to start service
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1731)
        at org.jboss.msc.service.ServiceControllerImpl$ControllerTask.run(ServiceControllerImpl.java:1559)
        at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
        at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1990)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1363)
        at java.lang.Thread.run(Thread.java:750)
Caused by: java.lang.IllegalArgumentException: UT000220: The AJP listener is configured to require secret but the secret is either null or empty string. This combination is not allowed.
        at io.undertow.server.protocol.ajp.AjpOpenListener.createAjpRequestParser(AjpOpenListener.java:205)
        at io.undertow.server.protocol.ajp.AjpOpenListener.<init>(AjpOpenListener.java:114)
        at org.wildfly.extension.undertow.AjpListenerService.createOpenListener(AjpListenerService.java:60)
        at org.wildfly.extension.undertow.ListenerService.start(ListenerService.java:177)
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1739)
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1701)
        ... 6 more

ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("add") failed - address: ([
    ("subsystem" => "undertow"),
    ("server" => "default-server"),
    ("ajp-listener" => "ajp")
]) - failure description: {"WFLYCTL0080: Failed services" => {"org.wildfly.undertow.listener.ajp" => "Failed to start service
    Caused by: java.lang.IllegalArgumentException: UT000220: The AJP listener is configured to require secret but the secret is either null or empty string. This combination is not allowed."}}

• JBoss EAP 7.4.23 got patched to 7.4.25 and not starting anymore.

2026-08-19 08:52:32,170 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-6) MSC000001: Failed to start service org.wildfly.undertow.listener.ajp: org.jboss.msc.service.StartException in service org.wildfly.undertow.listener.ajp:
Failed to start service
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1731)
        at org.jboss.msc.service.ServiceControllerImpl$ControllerTask.run(ServiceControllerImpl.java:1559)
        at org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
        at org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1990)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
        at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1363)
        at java.lang.Thread.run(Thread.java:750)
Caused by: java.lang.IllegalArgumentException: UT000220: The AJP listener is configured to require secret but the secret is either null or empty string. This combination is not allowed.
        at io.undertow.server.protocol.ajp.AjpOpenListener.createAjpRequestParser(AjpOpenListener.java:205)
        at io.undertow.server.protocol.ajp.AjpOpenListener.<init>(AjpOpenListener.java:114)
        at org.wildfly.extension.undertow.AjpListenerService.createOpenListener(AjpListenerService.java:60)
        at org.wildfly.extension.undertow.ListenerService.start(ListenerService.java:177)
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1739)
        at org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1701)
        ... 6 more