In Valve Steam Client for Windows through 2019-08-07, HKLM\SOFTWARE\Wow6432Node\Valve\Steam has explicit "Full control" for the Users group, which allows local users to gain NT AUTHORITY\SYSTEM access.
https://habr.com/ru/company/pm/blog/462479/
https://github.com/alexanderbittner/steam-privesc/
https://amonitoring.ru/article/steamclient-0day/
Source: Mitre, NVD
Published: 2019-08-07
Updated: 2026-06-17
Base Score: 7.2
Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C
Severity: High
Base Score: 6.6
Vector: CVSS:3.0/AV:P/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: Medium
EPSS: 0.00053