ED 20-04: Mitigate Netlogon Elevation of Privilege Vulnerability from August 2020 Patch Tuesday
This page contains a web-friendly version of the Cybersecurity and Infrastructure Security Agency’s Emergency Directive 20-04, “Mitigate Netlogon Elevation of Privilege Vulnerability from August 2020 Patch Tuesday”.
Section 3553(h) of title 44, U.S. Code, authorizes the Secretary of Homeland Security, in response to a known or reasonably suspected information security threat, vulnerability, or incident that represents a substantial threat to the information security of an agency, to “issue an emergency directive to the head of an agency to take any lawful action with respect to the operation of the information system, including such systems used or operated by another entity on behalf of an agency, that collects, processes, stores, transmits, disseminates, or otherwise maintains agency information, for the purpose of protecting the information system from, or mitigating, an information security threat.” 44 U.S.C. § 3553(h)(1)–(2).
Section 2205(3) of the Homeland Security Act of 2002, as amended, delegates this authority to the Director of the Cybersecurity and Infrastructure Security Agency. 6 U.S.C. § 655(3).
Federal agencies are required to comply with these directives. 44 U.S.C. § 3554 (a)(1)(B)(v).
These directives do not apply to statutorily-defined “national security systems” nor to systems operated by the Department of Defense or the Intelligence Community. 44 U.S.C. § 3553(d), (e)(2), (e)(3), (h)(1)(B).
On August 11, 2020, Microsoft released a software update to mitigate a critical vulnerability in Windows Server operating systems (CVE-2020-1472). The vulnerability in Microsoft Windows Netlogon Remote Protocol (MS-NRPC), a core authentication component of Active Directory, could allow an unauthenticated attacker with network access to a domain controller to completely compromise all Active Directory identity services.
Applying the update released on August 11 to domain controllers is currently the only mitigation to this vulnerability (aside from removing affected domain controllers from the network).
CISA has determined that this vulnerability poses an unacceptable risk to the Federal Civilian Executive Branch and requires an immediate and emergency action. This determination is based on the following:
- the availability of the exploit code in the wild increasing likelihood of any upatched domain controller being exploited;
- the widespread presence of the affected domain controllers across the federal enterprise;
- the high potential for a compromise of agency information systems;
- the grave impact of a successful compromise; and
- the continued presence of the vulnerability more than 30 days since the update was released.
CISA requires that agencies immediately apply the Windows Server August 2020 security update to all domain controllers.
This emergency directive requires the following actions:
Update all Windows Servers with the domain controller role by 11:59 PM EDT, Monday, September 21, 2020,
Apply the August 2020 Security Update to all Windows Servers with the domain controller role. If affected domain controllers cannot be updated, ensure they are removed from the network.
By 11:59 PM EDT, Monday, September 21, 2020, ensure technical and/or management controls are in place to ensure newly provisioned or previously disconnected domain controller servers are updated before connecting to agency networks.
In addition to agencies using their vulnerability scanning tools for this task, CISA recommends that agencies use other means to confirm that the update has been properly deployed.
These requirements apply to Windows Servers with the Active Directory domain controller role in any information system, including an information system used or operated by another entity on behalf of an agency, that collects, processes, stores, transmits, disseminates, or otherwise maintains agency information.
Report information to CISA
By 11:59 PM EDT, Wednesday, September 23, 2020, submit a completion report using the template provided below. Department-level Chief Information Officers (CIOs) or equivalents must submit completion reports attesting to CISA that the applicable update has been applied to all affected servers and provide assurance that newly provisioned or previously disconnected servers will be patched as required by this directive prior to network connection (per Action 1).
- CISA will continue to work with our partners to monitor for active exploitation of this vulnerability.
- CISA will review and validate agency compliance and ensure that agencies participating in Continuous Diagnostic and Mitigation (CDM) program can leverage the support of their CDM system integrators (SIs) to assist with this effort, if needed. If agencies want to enlist the help of their CDM SIs, please notify your CDM Portfolio Team.
- CISA will provide additional guidance to agencies via the CISA website, through an emergency directive issuance coordination call, and through individual engagements upon request (via CyberDirectives@cisa.dhs.gov).
Beginning October 1, 2020, the CISA Director will engage the CIOs and/or Senior Agency Officials for Risk Management (SAORM) of agencies that have not completed required actions, as appropriate and based on a risk-based approach.
- By October 5, 2020, CISA will provide a report to the Secretary of Homeland Security and the Director of Office of Management and Budget (OMB) identifying cross-agency status and outstanding issues.
This emergency directive remains in effect until all agencies have applied the August 2020 Security Update (or other superseding updates) or the directive is terminated through other appropriate action.
- General information, assistance, and reporting – CyberDirectives@cisa.dhs.gov
- Reporting indications of potential compromise – Central@cisa.gov
Frequently Asked Questions
Who is required to take this action under this directive?
The full list of agencies in scope of this directive is at Federal Civilian Executive Branch Agencies List. Though CISA directives are not mandatory for any other organizations, CISA publishes alerts and implementation guidance to support broader stakeholder efforts. State, local, tribal, and territorial governments, critical infrastructure, and other non-government organizations are encouraged to review and deploy this critical patch.
Does this directive apply to all Windows Servers or only those with the controller role?
Only to Windows Servers with the Active Directory domain controller role.
Who is responsible for updating servers in externally hosted systems (like cloud)?
- If the server belongs to a service provider and is only supporting the agency infrastructure (e.g., cloud service provider, PaaS and SaaS, management network, etc.), then the service provider is responsible for patching and reporting to your agency.
- If the server with the domain controller role is your authorization to operate (ATO) boundary (and accompanying inventory), then it falls into the scope of the directive and you are responsible for updating the server and reporting on it.
What are some technical and/or management controls to restrict unpatched endpoints from connecting to networks?
An example of a technical control is network access control (NAC), which can quarantine devices that do not meet agency ‘health’ standards (e.g., missing patches). Management controls may include policies and manual procedures that prohibit unpatched endpoints from being connected to agency networks until patched.
What other information is available to agencies to assist with scanning and remediation?
CISA does not endorse any particular vendor, though agencies using CDM capabilities that include Splunk tools may their blog post useful.