The IIS 8.5 websites connectionTimeout setting must be explicitly configured to disconnect an idle session.

From IIS 8.5 Site Security Technical Implementation Guide

Part of SRG-APP-000295-WSR-000134

Associated with: CCI-002361

SV-91537r2_rule The IIS 8.5 websites connectionTimeout setting must be explicitly configured to disconnect an idle session.

Vulnerability discussion

Leaving sessions open indefinitely is a major security risk. An attacker can easily use an already authenticated session to access the hosted application as the previously authenticated user. By closing sessions after a set period of inactivity, the web server can make certain that those sessions that are not closed through the user logging out of an application are eventually closed.Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications.

Check content

Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Click the site name. Select "Configuration Editor" under the "Management" section. From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState". Verify the "timeout" is set to "00:20:00 or less”, using the lowest value possible depending upon the application. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications. If "timeout" is not set to "00:20:00 or less”, this is a finding.

Fix text

Follow the procedures below for each site hosted on the IIS 8.5 web server: Open the IIS 8.5 Manager. Click the site name. Select "Configuration Editor" under the "Management" section. From the "Section:" drop-down list at the top of the configuration editor, locate "system.web/sessionState". Set the "timeout" to "00:20:00 or less”, using the lowest value possible depending upon the application. Acceptable values are 5 minutes for high-value applications, 10 minutes for medium-value applications, and 20 minutes for low-value applications. In the "Actions" pane, click "Apply".

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