ZAP 2.16.1 Hangs/Freezes on Initialization on Headless Ubuntu 24

[ZAP user]

Hello,

I'm having an issue where ZAP hangs during startup on a headless Ubuntu 24 server. It loads all the add-ons and then freezes completely without any error messages.

My Environment:

• OS: Ubuntu 24.04 LTS

• ZAP Version: 2.16.1

• Java Version: 21.0.8 (from ZAP's log)

• Mode: Headless / Daemon

Steps to Reproduce: I'm running ZAP directly in the foreground to debug the issue with this command:

Bash

/usr/local/zaproxy/zap.sh -daemon -host 0.0.0.0 -port 8080 -config api.disablekey=true

Observed Behavior: The initialization log prints out, showing all add-ons being loaded. It then stops and hangs indefinitely after the final add-on log message (Initializing OAST Scripts).

• There are no error messages or crash reports.

• The process remains active but consumes no CPU.

• The API port (8080) never opens (confirmed with ss -ltnp).

Log File: Here is the full log from zap.log until the point where it hangs:

```Found Java version 21.0.8 

Available memory: 3819 MB 

Using JVM args: -Xmx4g 629 [

main] WARN org.zaproxy.zap.ZapBootstrap - ZAP is being run using the root user - this is NOT recommended! 644 

[main] INFO org.zaproxy.zap.DaemonBootstrap - ZAP 2.16.1 started 05/09/2025, 07:20:00 with home: /root/.ZAP/ cores: 4 maxMemory: 4 GB ... (log content from your file) ... 4082 

[ZAP-daemon] INFO org.parosproxy.paros.extension.ExtensionLoader - Initializing Out-of-band Application Security Testing - Adds Out-of-band Application Security Testing functionality. 4086 

[ZAP-daemon] INFO org.parosproxy.paros.extension.ExtensionLoader - Initializing OAST Scripts - Adds OAST scripts. <-- HANGS HERE -->```

Has anyone else experienced this with a similar setup? Is this a known issue, or is there anything else I could check?

Thanks for your help!

[kingthorin+zap]

Is it able to start headed?

Could you capture a thread dump while it appears to be hung? (https://www.baeldung.com/java-thread-dump)

Oh looking at the startup you've asked it to allocate 4GB or RAM while only 3GB is available.