Title

MIME sniffing must be disallowed (Restricted Sites zone). (Cat II impact)

Discussion

This policy setting allows you to manage MIME sniffing for file promotion from one type to another based on a MIME sniff. A MIME sniff is the recognition by Internet Explorer of the file type based on a bit signature. If you enable this policy setting, the MIME Sniffing Safety Feature will not apply in this zone. The security zone will run without the added layer of security provided by this feature. If you disable this policy setting, the actions that may be harmful cannot run; this Internet Explorer security feature will be turned on in this zone, as dictated by the feature control setting for the process. If you do not configure this policy setting, the MIME Sniffing Safety Feature will not apply in this zone.

Check Content

The policy value for Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Security Page -> Restricted Sites Zone -> "Enable MIME Sniffing" must be "Enabled", and "Disable" selected from the drop-down box. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\4 Criteria: If the value 2100 is REG_DWORD = 3, this is not a finding.

Fix Text

Set the policy value for Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Security Page -> Restricted Sites Zone -> "Enable MIME Sniffing" to "Enabled", and select "Disable" from the drop-down box.

Additional Identifiers

Rule ID: SV-45278r1_rule

Vulnerability ID: V-15524

Group Title: DTBI470 - MIME sniffing - Restricted

Expert Comments

CCIs tied to check.

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