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

From Microsoft Internet Explorer 11 Security Technical Implementation Guide

Part of DTBI1100-IE11-Allow Fallback to SSL 3.0 (Internet Explorer)

SV-79219r3_rule Allow Fallback to SSL 3.0 (Internet Explorer) must be disabled.

Vulnerability discussion

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 1.0 or greater fails.

Check content

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

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.

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