For details see https://www.chaitin.cn/en/ghostcat

To see if you have the issue run: netstat -ntpl | grep 8009 and it will list the process listening on that port.  Check if it is bound to the public IP address (vs. a localhost IP address).

To mitigate the issue add an address="127.0.0.1" attribute to the Tomcat Connector for port 8009.

If you have Tomcat in /usr/local/tomcat; then edit /usr/local/tomcat/conf/server.xml

Change:
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />

To:

<Connector port="8009" address="127.0.0.1" protocol="AJP/1.3" redirectPort="8443" />

Then restart tomcat; e.g. with /etc/init.d/tomcat restart

Then re-check the ports that you have open and make sure port 8009 is only available from the local IP.  e.g.
# netstat -ntpl | grep 8009
tcp6 0 0 127.0.0.1:8009 :::* LISTEN 11615/java

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