'Certighost' Flaw Haunts Microsoft Active Directory Certificates

July 28, 2026 · Dark Reading · Severity: HIGH

Microsoft patched a high-severity vulnerability in Active Directory Certificate Services (AD CS) that could enable attackers to conduct certificate-based attacks against domain environments. The Certighost flaw, as it came to be known, threatened the foundation of certificate-based authentication in Active Directory, potentially allowing adversaries to forge certificates, escalate privileges, or impersonate domain entities. Since AD CS underpins smart card authentication, VPN certificates, code signing, and Windows Hello for Business, exploitation could give attackers persistent, cryptographically trusted access that bypasses traditional password and MFA controls entirely.