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Double encoded URL requests must be prohibited by any IIS 10.0 website.


Overview

Finding ID Version Rule ID IA Controls Severity
V-218757 IIST-SI-000229 SV-218757r558649_rule Medium
Description
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.
STIG Date
Microsoft IIS 10.0 Site Security Technical Implementation Guide 2021-12-28

Details

Check Text ( C-20230r311169_chk )
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 (F-20228r311170_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 double escaping" check box.