CVE-2025-21311: Windows NTLM V1 Elevation of Privilege Vulnerability

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigations might apply in your situation:

Set the LmCompatabilityLvl to its maximum value (5) for all machines. This will prevent the usage of the older NTLMv1 protocol, while still allowing NTLMv2. Please see Network security: LAN Manager authentication level for more information.