Insufficiently protected credentials in Microsoft Windows and Windows Server - CVE-2026-121680

Vulnerability details

The vulnerability allows a remote attacker to obtain a victim's Net-NTLMv2 hash and potentially authenticate as the victim.

The vulnerability exists due to insufficient protection of credentials in Windows NTLM when connecting to an untrusted network location. A remote attacker can send a specially crafted email that causes the victim's system to connect to an attacker-controlled location, exposing the victim's Net-NTLMv2 hash, which can then be relayed to another service to authenticate as the victim.

Affected software

How to mitigate CVE-2026-121680

External References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2026-121680
• https://support.microsoft.com/help/5131291

Related Security Bulletins

• Multiple vulnerabilities in Microsoft Windows