Microsoft IIS 10.0 Site Security

Unspecified file extensions on a production IIS 10.0 web server must be removed

STIG ID: IIST-SV-000158 | SRG: SRG-APP-000516-WSR-000174 | Severity: Medium | CCI: CCI-000366 | Vulnerability ID: V-218824

Description

By allowing unspecified file extensions to execute, the web servers attack surface is significantly increased. This increased risk can be reduced by only allowing specific ISAPI extensions or CGI extensions to run on the web server.

Check

C-218824r961863_chk

Open the IIS 10.0 Manager.Click the IIS 10.0 web server name.Double-click the "ISAPI and CGI restrictions" icon.Click “Edit Feature Settings".Verify the "Allow unspecified CGI modules" and the "Allow unspecified ISAPI modules" boxes are NOT ed.If either or both of the "Allow unspecified CGI modules" and the "Allow unspecified ISAPI modules" boxes are ed, this is a finding.

Fix

F-20294r310948_fix

Open the IIS 10.0 Manager.Click the IIS 10.0 web server name.Double-click the "ISAPI and CGI restrictions" icon.Click "Edit Feature Settings".Remove the check from the "Allow unspecified CGI modules" and the "Allow unspecified ISAPI modules" check boxes.Click "OK".