Windows Server 2025 Internet Protocol version 6 (IPv6) source routing must be configured to the highest protection level to prevent IP source routing.

STIG ID: WN25-CC-000030  |  SRG: SRG-OS-000480-GPOS-00227 |  Severity: low (CAT III)  |  CCI: CCI-000366 |  Vulnerability Id: V-278082

Vulnerability Discussion

Configuring the system to disable IPv6 source routing protects against spoofing.

Check

Verify the registry value below:

Registry Hive: HKEY_LOCAL_MACHINE
Registry Path: \SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\

Value Name: DisableIPSourceRouting

Type: REG_DWORD
Value: 0x00000002 (2)

If the registry value does not exist or is not configured as specified, this is a finding.

Fix

Configure the policy value for Computer Configuration >> Administrative Templates >> MSS (Legacy) >> MSS: (DisableIPSourceRouting IPv6) IP source routing protection level (protects against packet spoofing) to "Enabled" with "Highest protection, source routing is completely disabled" selected.

This policy setting requires the installation of the MSS-Legacy custom templates included with the STIG package. "MSS-Legacy.admx" and "MSS-Legacy.adml" must be copied to the \Windows\PolicyDefinitions and \Windows\PolicyDefinitions\en-US directories respectively.
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