Allow Fallback to SSL 3.0 (Internet Explorer) must be disabled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-64729	DTBI1100-IE11	SV-79219r3_rule		Medium

Description
This parameter ensures only DoD-approved ciphers and algorithms are enabled for use by the web browser by blocking an insecure fallback to SSL when TLS 1.1 or greater fails.

STIG	Date
Microsoft Internet Explorer 11 Security Technical Implementation Guide	2017-03-01

Details

Check Text ( C-65471r4_chk )
The policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" must be "Enabled", and "No Sites" selected from the drop-down box. If "Allow fallback to SSL 3.0 (Internet Explorer)" is not "Enabled" or any other drop-down option is selected, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings. Criteria: If the value "EnableSSL3Fallback" is REG_DWORD=0, this is not a finding.

Check Text ( C-65471r4_chk )

The policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" must be "Enabled", and "No Sites" selected from the drop-down box. If "Allow fallback to SSL 3.0 (Internet Explorer)" is not "Enabled" or any other drop-down option is selected, this is a finding.

Procedure: Use the Windows Registry Editor to navigate to the following key:

HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings.

Criteria: If the value "EnableSSL3Fallback" is REG_DWORD=0, this is not a finding.

Fix Text (F-70659r5_fix)
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" to "Enabled", and select "No Sites" from the drop-down box.