Title

Internet calendar integration in Outlook must be disabled. (Cat II impact)

Discussion

This policy setting allows the user to determine whether or not to include Internet Calendar integration in Outlook. The Internet Calendar feature in Outlook enables users to publish calendars online (using the webcal:// protocol) and subscribe to calendars that others have published. When users subscribe to an internet calendar, Outlook queries the calendar at regular intervals and downloads any changes as they are posted. If this policy setting is enabled, all internet calendar functionality in Outlook is disabled. If this policy setting is disabled or not configured, Outlook allows users to subscribe to trusted and untrusted internet calendars. The webcal protocol also has a history of loading web sites vulnerable to cross site scripting.

Check Content

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Account Settings >> Internet Calendars "Do not include Internet Calendar integration in Outlook" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\webcal Criteria: If the value Disable is REG_DWORD = 1, this is not a finding.

Fix Text

Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Account Settings >> Internet Calendars "Do not include Internet Calendar integration in Outlook" to "Enabled".

Additional Identifiers

Rule ID: SV-228470r822351_rule

Vulnerability ID: V-228470

Group Title: SRG-APP-000141

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.