Patch by Tonight: CISA Issues Emergency Directive for Critical Netlogon Flaw

The US Department of Homeland Security's Cybersecurity and Infrastructure Security Agency (CISA) has published an emergency directive requiring federal agencies to mitigate a critical vulnerability in the Microsoft Windows Netlogon Remote Protocol (MS-NRPC), a core authentication component of Active Directory.

"CISA has determined that this vulnerability poses an unacceptable risk to the Federal Civilian Executive Branch and requires an immediate and emergency action," officials state. The agency last week issued an alert for the flaw following the discovery of publicly available exploit code.  

CVE-2020-1472, also called "Zerologon," has a CVSS score of 10 and is categorized as Critical by Microsoft. It exists when an attacker creates a vulnerable Netlogon secure channel connection to a domain controller using MS-NRPC. With that connection, they don't need to authenticate in order to elevate privileges and become an admin. Microsoft patched the bug back in August; it will be fully addressed in a two-part rollout. 

Emergency directive 20-04 requires federal agencies to update all Windows Servers with the domain controller role by midnight on Sept. 21. If affected controllers cannot be updated, agencies are instructed to remove them from the network. They must also ensure technical and management controls are in place to make sure newly provisioned or previously disconnected domain controller servers are updated before they're connected to agency networks.

CISA did not describe any known attacks weaponizing the vulnerability; however, its issuance of an emergency directive indicates great concern for potential attacks. While ED 20-04 only applies to Executive Branch departments and agencies, CISA "strongly recommends" state and local governments, the private sector, and other organizations patch this as soon as possible. 

Read the full directive for more details.