The IIS 10.0 web server must have Multipurpose Internet Mail Extensions (MIME) that invoke OS shell programs disabled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-100131	IIST-SV-000124	SV-109235r1_rule		Medium

Description
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 the type of program, various file types, and extensions 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 to ensure hosted application users do not have access to these programs. Shell programs may execute shell escapes and can perform unauthorized activities that could damage the security posture of the web server.

Description

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 the type of program, various file types, and extensions 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 to ensure hosted application users do not have access to these programs. Shell programs may execute shell escapes and can perform unauthorized activities that could damage the security posture of the web server.

STIG	Date
Microsoft IIS 10.0 Server Security Technical Implementation Guide	2020-06-08

Details

Check Text ( C-98983r1_chk )
Open the IIS 10.0 Manager. Click the IIS 10.0 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.

Check Text ( C-98983r1_chk )

Open the IIS 10.0 Manager.

Click the IIS 10.0 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 (F-105817r1_fix)
Open the IIS 10.0 Manager. Click the IIS 10.0 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".