Security Vulnerability: Zerologon aka CVE-2020-1472

This document (000019713) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12

Situation

The issue itself lies within the Netlogon Remote Protocol, that is used, among other things, to update passwords remotely. By sending Netlogon messages filled with zeroes in certain fields, an attacker can change the domain controller password and gain full access to the AD.

As this is a protocol design flaw inside the cryptographic authentication method, the issue is present in Samba.

Resolution

To prevent an attack the Samba server has to be run with the 'server schannel = yes' switch that is set by default since Samba 4.8.

Mitigations:
Every Samba administrator should check the server settings for 'server schannel' values.

Please note the following settings are NOT secure and could lead to a fully compromised domain controller :

server schannel = no
server schannel = auto

Please use the setting below as current mitigation :

server schannel = yes

As per September 23, 2020. SUSE has released updates for all effected code streams.

Cause

CVE-2020-1472

Status

Security Alert

Additional Information

Reference(s) :

https://www.secura.com/blog/zero-logon

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.