Improper Encoding or Escaping of Output and Injection in LibreNMS

An issue was discovered in LibreNMS 1.50.1. The scripts that handle graphing options (includes/html/graphs/common.inc.php and includes/html/graphs/graphs.inc.php) do not sufficiently validate or encode several fields of user supplied input. Some parameters are filtered with mysqli_real_escape_string, which is only useful for preventing SQL injection attacks; other parameters are unfiltered. This allows an attacker to inject RRDtool syntax with newline characters via the html/graph.php and html/graph-realtime.php scripts. RRDtool syntax is quite versatile and an attacker could leverage this to perform a number of attacks, including disclosing directory structure and filenames, disclosing file content, denial of service, or writing arbitrary files. NOTE, relative to CVE-2019-10665, this requires authentication and the pathnames differ.