Title

The system is not configured to use Safe DLL Search Mode. (Cat II impact)

Discussion

The default search behavior, when an application calls a function in a Dynamic Link Library (DLL), is to search the current directory followed by the directories contained in the systems path environment variable. An unauthorized DLL inserted into an applications working directory could allow malicious code to be run on the system. Creating the following registry key and setting the appropriate value forces the system to search the %Systemroot% for the DLL before searching the current directory or the rest of the path.

Check Content

Analyze the system using the Security Configuration and Analysis snap-in. Expand the Security Configuration and Analysis tree view. Navigate to Local Policies -> Security Options. If the value for “MSS: (SafeDllSearchMode) Enable Safe DLL search mode (recommended)” is not set to “Enabled”, then this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \System\CurrentControlSet\Control\Session Manager\ Value Name: SafeDllSearchMode Value Type: REG_DWORD Value: 1

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “MSS: (SafeDllSearchMode) Enable Safe DLL search mode (recommended)” to “Enabled”.

Additional Identifiers

Rule ID: SV-3479r1_rule

Vulnerability ID: V-3479

Group Title: Safe DLL Search Mode

Expert Comments

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