Non-ASCII characters in URLs must be prohibited by any IIS 10.0 website.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-218756	SRG-APP-000246-WSR-000149	IIST-SI-000228	SV-218756r961152_rule	2025-02-11	2

Description
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.

ℹ️ Check
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.

ℹ️ Check

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
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.