TMA-IIS-4.3

Ensure 'MaxQueryString request filter' is configured

LowLevel 2Automatediis

Description

The MaxQueryString Request Filter describes the upper limit on the length of the query string that the configured IIS server will allow for websites or applications. It is recommended that values always be established to limit the amount of data that can be accepted in the query string. requestLimits maxQueryString must be 2048 or lower at server level and for every site (default 2048). PowerShell 5.1 with the WebAdministration module; run elevated.

How it is checked

Audit method: Shell command

shell

Import-Module WebAdministration -ErrorAction Stop; $paths = @('MACHINE/WEBROOT/APPHOST') + @(Get-Website | ForEach-Object { "IIS:\Sites\$($_.Name)" }); $bad = @($paths | Where-Object { $c = Get-WebConfiguration -Filter 'system.webServer/security/requestFiltering/requestLimits' -PSPath $_; [long]$c.maxQueryString -gt 2048 }); if ($bad.Count -eq 0) { 'compliant' } else { 'noncompliant' }

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Set-WebConfigurationProperty -PSPath 'MACHINE/WEBROOT/APPHOST' -Filter system.webServer/security/requestFiltering/requestLimits -Name maxQueryString -Value 2048

Properties

Operating systems: Any
Tags: iisrequest-filtering
Reference: CIS Microsoft IIS 10 Benchmark v1.2.1 - 4.3 Ensure 'MaxQueryString request filter' is configured

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target iis --level 2