A security feature bypass vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLMv2 protection if a client is also sending LMv2 responses, aka 'Windows NTLM Security Feature Bypass Vulnerability'.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-1338
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1338