secure_file_priv

The secure_file_priv variable is used to determine where to read/write files from. An empty value lets us read files from the entire file system. Otherwise, if a certain directory is set, we can only read from the folder specified by the variable. On the other hand, NULL means we cannot read/write from any directory. MariaDB has this variable set to empty by default, which lets us read/write to any file if the user has the FILE privilege. However, MySQL uses /var/lib/mysql-files as the default folder. This means that reading files through a MySQL injection isn't possible with default settings. Even worse, some modern configurations default to NULL, meaning that we cannot read/write files anywhere within the system.

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