Researchers Uncover How Outlook Vulnerability Could Leak Your NTLM Passwords

A patched Outlook vulnerability (CVE-2023-35636, CVSS 6.5) allowed specially crafted files—delivered via email or hosted web content and leveraging calendar-sharing headers—to exfiltrate NTLM v2 hashed credentials; researcher Dolev Taler demonstrated leaks using Windows Performance Analyzer and File Explorer (those methods remain unpatched), enabling relay or offline brute-force attacks, and Microsoft addressed the issue in its December 2023 Patch Tuesday updates.