Title

Double encoded URL requests must be prohibited by any IIS 10.0 website. (Cat II impact)

Discussion

Request filtering enables administrators to create a more granular rule set with which to allow or reject inbound web content. Setting limits on web requests ensures availability of web services and mitigates the risk of buffer overflow type attacks. When the "Allow double escaping" option is disabled, it prevents attacks that rely on double-encoded requests.

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 double escaping" check box is checked, this is a finding.

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 double escaping" check box.

Additional Identifiers

Rule ID: SV-218757r558649_rule

Vulnerability ID: V-218757

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.