The affected asset is vulnerable to this vulnerability ONLY if it is running one of the following modules: mod_session. Review your web server configuration for validation. When mod_session is configured to forward its session data to CGI applications (SessionEnv on, not the default), a remote user may influence their content by using a "Session" header. This comes from the "HTTP_SESSION" variable name used by mod_session to forward its data to CGIs, since the prefix "HTTP_" is also used by the Apache HTTP Server to pass HTTP header fields, per CGI specifications. The severity is set to Moderate because "SessionEnv on" is not a default nor common configuration, it should be considered more severe when this is the case though, because of the possible remote exploitation.