CVE-2025-21311: 
vulnerability analysis and mitigation

Windows NTLM V1 Elevation of Privilege Vulnerability (CVE-2025-21311) is a critical vulnerability discovered in January 2025 affecting Windows NTLMv1 authentication protocol. The vulnerability has received a CVSS score of 9.8, indicating its critical severity. It affects various Windows systems including Windows 11 Version 24H2 and Windows Server 2022 23H2 Edition (NVD).

The vulnerability exists in the NT LAN Manager (NTLM) V1 authentication protocol. It is characterized by its low attack complexity, meaning attackers need minimal system knowledge and can consistently succeed with their payload against the vulnerable component. The vulnerability is remotely exploitable from the internet and has received a Critical CVSS score of 9.8 (CrowdStrike).

This critical elevation of privilege vulnerability could allow an attacker to gain elevated system privileges. The vulnerability's high CVSS score of 9.8 indicates potential severe impacts on system confidentiality, integrity, and availability. Being remotely exploitable from the internet makes it particularly dangerous for exposed systems (CrowdStrike).

To mitigate this vulnerability, it is recommended to set LmCompatibilityLevel to its maximum value (5) on all machines, which disables the older NTLMv1 protocol while retaining NTLMv2 functionality. Microsoft has released patches for affected systems, and users are strongly advised to apply these updates (CrowdStrike).