Logstash syslog input filter default grok patterns

What are the default grok patterns for the syslog input filter?

The data is from old snare, failing messages are formatted something like this:

<135> 07/18/2022:18:14:52 GMT HOSTNAME syslog_message.

Thanks

The default value depends on ecs_compatibility. It is set here. The SYSLOGLINE pattern is defined either here or here. I very much doubt it will match that date format with a timezone. You will need to write your own pattern.