Researchers have released a proof-of-concept (PoC) exploit for 'Zerologon' Windows vulnerability, which, if left unpatched, could allow an attacker with foothold on the local network to instantly become Domain Admin and enjoy access to an organisation's Active Directory domain controllers.
The PoC exploit for the vulnerability, tracked as CVE-2020-1472, has been published on GitHub by security researcher Dirk-jan Mollenma.
The 'Zerologon' bug was patched by Microsoft last month, although the company did not reveal full details of the flaw at the time.
Secura's security expert Tom Tervoort, who is credited for discovering the flaw and reporting it to Microsoft, has now published a detailed post revealing the full impact and execution of the bug.
According to Tervoort, CVE-2020-1472 is an elevation of privilege bug in Netlogon Remote Protocol (MS-NRPC) which is used to authenticate users against domain controllers.
The vulnerability arises due to a flaw in cryptographic algorithm used in the Netlogon authentication process. This flaw lets an attacker to impersonate any computer and run remote procedure calls on their behalf.
To exploit the bug, an attacker must already have a foothold inside a targeted network. From there, they can send a string of zeros in a series of messages using the Netlogon protocol to fill various fields. This enables them to modify the Active Directory stored password of a Domain Controller.
After successfully exploiting the vulnerability, the attackers could run a specially crafted application on a device on the network.
According to Tervoort, the attacker can exploit the bug and gain admin credentials, as long as they are able to establish TCP links with a vulnerable domain controller.
The vulnerability has received the full score of 10 out of 10 on Common Vulnerability Scoring System (CVSS) rating.
Microsoft said last month that it would address the bug in a phased two-part rollout. These updates will address the vulnerability "by modifying how Netlogon handles the usage of Netlogon secure channels."
Last month, the company released the initial temporary fix for the Zerologon attack.
"Customers who apply the update, or have automatic updates enabled, will be protected," Microsoft said at the time.
The second phase of Windows updates is expected to be available in February next year, and in that update, the enforcement mode for NRP will be turned on by default.
Meanwhile, Secura has published a Python script on Github that admins can use to test if the Domain Controller they use is vulnerable.
Chinese state-sponsored cyber actors are targeting bugs in F5, Citrix, Pulse and Microsoft Exchange Servers, US agencies warn
Organisations need to patch their systems immediately, they advise
Chinese intelligence is building detailed profiles on tens of thousands of citizens worldwide, leaked database suggests
Names include 52,000 Americans, 35,000 Australians, 10,000 Indians, 9,700 British, 5,000 Canadians, 1,400 Malaysians and 793 New Zealanders
The attack seems to have infected business systems, not data centres software
Join us to learn about the newest techniques deployed by attackers
Twenty-three are rated as 'Critical', many affect SharePoint