Microsoft released an alert on a couple of Active Directory vulnerabilities, that have been fixed with the November 2021 Patch Tuesday security updates, that could allow threat actors to takeover Windows domains.
The flaws, tracked as CVE-2021-42287 and CVE-2021-42278, can be chained to impersonate domain controllers and gain administrative privileges on Active Directory.
Microsoft is now warning customers to address both issues immediately due to the public availability of Proof-of-concept exploit code. The IT giant also published a guide to help customers in detecting the attempts of exploitation of both issues.
“Both vulnerabilities are described as a ‘Windows Active Directory domain service privilege escalation vulnerability’.A few weeks later, on December 12, 2021, a proof-of-concept tool leveraging these vulnerabilities was publicly disclosed.” states Microsoft. “When combining these two vulnerabilities, an attacker can create a straightforward path to a Domain Admin user in an Active Directory environment that hasn’t applied these new updates. This escalation attack allows attackers to easily elevate their privilege to that of a Domain Admin once they compromise a regular user in the domain.”
The CVE-2021-42278 vulnerability is a security bypass issue that allows potential attackers to impersonate a domain controller using computer account sAMAccountName spoofing.
Experts pointed out that sAMAccountName attributes usually end with “$” in their name. “$” was used to distinguish between user objects and computer objects. With default settings, a normal user has permission to modify a machine account (up to 10 machines) and as its owner, they also have the permissions to edit its sAMAccountName attribute.
