Title

Interactive scripts on the IIS 8.5 web server must have restrictive access controls. (Cat II impact)

Discussion

CGI is a programming standard for interfacing external applications with information servers, such as HTTP or web servers. CGI, represented by all upper case letters, should not be confused with the .cgi file extension. The .cgi file extension does represent a CGI script, but CGI scripts may be written in a number of programming languages (e.g., PERL, C, PHP, and JavaScript), each having their own unique file extension. The use of CGI scripts represent one of the most common and exploitable means of compromising a web server. By definition, CGI scripts are executable by the operating system of the host server. While access control is provided via the web service, the execution of CGI programs is not limited unless the SA or the Web Manager takes specific measures. CGI programs can access and alter data files, launch other programs, and use the network.

Check Content

Determine whether scripts are used on the web server for the subject website. Common file extensions include, but are not limited to: .cgi, .pl, .vb, .class, .c, .php, .asp, and .aspx. If the website does not utilize CGI, this finding is Not Applicable. All interactive programs must have restrictive permissions. Open the IIS 8.5 Manager. Right-click the IIS 8.5 web site name and select “Explore”. Search for the listed script extensions. Review the permissions to the CGI scripts and verify only the permissions listed, or more restrictive permissions are assigned. Administrators: FULL Web Administrators: FULL TrustedInstaller: FULL ALL APPLICATION PACKAGES: Read SYSTEM: FULL ApplicationPoolId: READ Custom Service Account: READ Users: READ If the permissions are less restrictive than listed above, this is a finding.

Fix Text

Determine whether scripts are used on the web server for the subject website. Common file extensions include, but are not limited to: .cgi, .pl, .vb, .class, .c, .php, .asp, and .aspx. If the website does not utilize CGI, this finding is NA. All interactive programs must have restrictive permissions. Open the IIS 8.5 Manager. Right-click the IIS 8.5 web server name and select “Explore”. Search for the listed script extensions. Set the permissions to the CGI scripts as follows: Administrators: FULL Web Administrators: FULL TrustedInstaller: FULL ALL APPLICATION PACKAGES: Read SYSTEM: FULL ApplicationPoolId: READ Custom Service Account: READ Users: READ

Additional Identifiers

Rule ID: SV-214494r879587_rule

Vulnerability ID: V-214494

Group Title: SRG-APP-000141-WSR-000087

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.