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Unlisted file extensions in URL requests must be filtered by any IIS 10.0 website.

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-218758IIST-SI-000230SV-218758r1156527_ruleCCI-001094medium
Description
Request filtering enables administrators to create a more granular rule set to allow or reject inbound web content. Setting limits on web requests helps to ensure availability of web services and may also help mitigate the risk of buffer overflow type attacks. The allow unlisted property of the "File Extensions Request" filter enables rejection of requests containing specific file extensions not defined in the "File Extensions" filter. Tripping this filter will cause IIS to generate a Status Code 404.7.
STIGDate
Microsoft IIS 10.0 Site Security Technical Implementation Guide2026-05-23

Related Frameworks

1 mapping across 4 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (1) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

CAP-02Resource Priority
0.50
NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (16) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AC-3Access Enforcement
1.00
AC-6(10)Prohibit Non-privileged Users from Executing Privileged Functions
1.00
AC-6(8)Privilege Levels for Code Execution
1.00
CM-11(2)Software Installation with Privileged Status
1.00
CM-5(1)Automated Access Enforcement and Audit Records
1.00
CM-5(6)Limit Library Privileges
1.00
CM-6Configuration Settings
1.00
CM-7Least Functionality
1.00
CM-7(2)Prevent Program Execution
1.00
SC-18(1)Identify Unacceptable Code and Take Corrective Actions
1.00

+6 more (top 10 by confidence shown)

CCI1 mapping
CCI-001094
1.00
NIST CSF 2.00 mappings

No source states a mapping between these directly.

Also reachable in 4 hops (1) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

PR.IR-04
0.50

Details

Check Text (C-218758r1156527_chk)

Note: If the server being reviewed is hosting SharePoint, this is Not Applicable. Note: If the server being reviewed is hosting Network Device Enrollment Services (NDES), this is Not Applicable. Note: If the server being reviewed is hosting Azure DevOps (ADO), this is Not Applicable. 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 unlisted file name extensions" 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. Note: If this IIS 10.0 installation is supporting Splunk, this requirement is Not Applicable. Note: If this IIS 10.0 installation is supporting WSUS, this requirement is Not Applicable.

Fix Text (F-20229r311173_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 unlisted file extensions" check box.