Title

Non-ASCII characters in URLs must be prohibited by any IIS 10.0 website. (Cat II impact)

Discussion

Setting limits on web requests ensures availability of web services and mitigates the risk of buffer overflow type attacks. The allow high-bit characters Request Filter enables rejection of requests containing non-ASCII characters.

Check Content

Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name. Double-click the "Request Filtering" icon. Click "Edit Feature Settings" in the "Actions" pane. If the "Allow high-bit characters" check box is checked, this is a finding. Note: If this IIS 10.0 installation is supporting Microsoft Exchange, and not otherwise hosting any content, this requirement is Not Applicable.

Fix Text

Follow the procedures below for each site hosted on the IIS 10.0 web server: Open the IIS 10.0 Manager. Click the site name under review. Double-click the "Request Filtering" icon. Click "Edit Feature Settings" in the "Actions" pane. Uncheck the "Allow high-bit characters" check box.

Additional Identifiers

Rule ID: SV-218756r961152_rule

Vulnerability ID: V-218756

Group Title: SRG-APP-000246-WSR-000149

Expert Comments

CCIs tied to check.

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