Title

The IIS 8.5 web server must have Multipurpose Internet Mail Extensions (MIME) that invoke OS shell programs disabled. (Cat II impact)

Discussion

Controlling what a user of a hosted application can access is part of the security posture of the web server. Any time a user can access more functionality than is needed for the operation of the hosted application poses a security issue. A user with too much access can view information that is not needed for the user's job role, or the user could use the function in an unintentional manner. A MIME tells the web server what type of program, various file types, and extensions are and what external utilities or programs are needed to execute the file type. A shell is a program that serves as the basic interface between the user and the operating system, so hosted application users must not have access to these programs. Shell programs may execute shell escapes and can then perform unauthorized activities that could damage the security posture of the web server.

Check Content

Open the IIS 8.5 Manager. Click the IIS 8.5 web server name. Under IIS, double-click the “MIME Types” icon. From the "Group by:" drop-down list, select "Content Type". From the list of extensions under "Application", verify MIME types for OS shell program extensions have been removed, to include at a minimum, the following extensions: .exe .dll .com .bat .csh If any OS shell MIME types are configured, this is a finding.

Fix Text

Open the IIS 8.5 Manager. Click the IIS 8.5 web server name. Under IIS, double-click the “MIME Types” icon. From the "Group by:" drop-down list, select "Content Type". From the list of extensions under "Application", remove MIME types for OS shell program extensions, to include at a minimum, the following extensions: .exe .dll .com .bat .csh Under the "Actions" pane, click "Apply".

Additional Identifiers

Rule ID: SV-214413r879587_rule

Vulnerability ID: V-214413

Group Title: SRG-APP-000141-WSR-000081

Expert Comments

CCIs tied to check.

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