I found that in the past, the WordPress version 2.0.6 and earlier was vulnerable. The remote host fails to properly sanitize input to the
tb_id parameter of the
wp-trackback.php script before using it in database queries.
I didn't found any countermeasure for this somewhere or if the vulnerability is eliminated to version newer than 2.0.6.
I also found that PHP's
register_globals setting must be enabled and that the remote version of PHP needs to be older than 4.4.3 or 5.1.4 for this to be vulnerable.