Known as "Token Kidnapping".
Vulnerable component: Windows
CVSSv3 score: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls
The vulnerability allows a local attacker to gain elevated privileges on the target system.
The weakness exists due to incorrect placing of access control lists (ACLs) on threads in the current ThreadPool. By leveraging incorrect thread ACLs an attacker can access NetworkService or LocalService account, obtain elevated privileges and execute code with privileges of SYSTEM account.
Successful exploitation of the vulnerability results in privilege escalation allowing to execute arbitrary code and take complete control of an affected system.
Note: this vulnerability was being actively exploited.