Microsoft Windows Local Security Authority (LSA) Spoofing Vulnerability — Microsoft Windows Local Security Authority (LSA) contains a spoofing vulnerability allowing an unauthenticated attacker to call a method on the LSARPC interface and coerce the domain controller to authenticate against another server using NTLM.
CVE-2021-36942 is a critical Windows LSA spoofing vulnerability (CVSS 9.0) enabling unauthenticated attackers to coerce domain controllers into NTLM authentication against attacker-controlled servers. This facilitates credential relay attacks and domain compromise. With public exploits available, immediate patching of all Windows domain controllers and servers is essential for Saudi organizations.
IMMEDIATE ACTIONS:
1. Identify all Windows domain controllers and servers in your environment
2. Apply Microsoft security patches KB5004018 (Windows Server 2019/2016) or equivalent for your OS version immediately
3. Implement network segmentation to restrict LSARPC (port 135, 445) access to trusted networks only
4. Enable NTLM signing and sealing via Group Policy: Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options
5. Deploy Extended Protection for Authentication (EPA) where applicable
6. Monitor for suspicious LSARPC calls and NTLM relay attempts using Windows Event Viewer (Event ID 4624, 4625)
7. Implement LDAP signing requirements to prevent credential relay
8. Review and restrict service account permissions following least privilege principle
9. Enable Windows Defender for Advanced Threat Protection (ATP) monitoring
10. Conduct immediate vulnerability scan of all Windows systems using CVSS 9.0+ filter
الإجراءات الفورية:
1. تحديد جميع متحكمات ومخدمات Windows في بيئتك
2. تطبيق تصحيحات الأمان من Microsoft KB5004018 (Windows Server 2019/2016) أو ما يعادلها فورًا
3. تنفيذ تقسيم الشبكة لتقييد وصول LSARPC (المنفذ 135، 445) للشبكات الموثوقة فقط
4. تفعيل توقيع وتشفير NTLM عبر Group Policy: Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options
5. نشر Extended Protection for Authentication (EPA) حيث ينطبق
6. مراقبة استدعاءات LSARPC المريبة ومحاولات إعادة توجيه NTLM باستخدام Windows Event Viewer (Event ID 4624, 4625)
7. تنفيذ متطلبات توقيع LDAP لمنع إعادة توجيه بيانات الاعتماد
8. مراجعة وتقييد صلاحيات حسابات الخدمة وفقًا لمبدأ أقل امتياز
9. تفعيل Windows Defender for Advanced Threat Protection (ATP)
10. إجراء فحص فوري للثغرات على جميع أنظمة Windows باستخدام مرشح CVSS 9.0+