An issue was discovered in Valve Steam Client 2.10.91.91. The installer allows local users to gain NT AUTHORITYSYSTEM privileges because some parts of %PROGRAMFILES(X86)%Steam and/or %COMMONPROGRAMFILES(X86)%Steam have weak permissions during a critical time window. An attacker can make this time window arbitrarily long by using opportunistic locks.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15530
Reference (s):
- http://daniels-it-blog.blogspot.com/2020/07/steam-arbitrary-code-execution-part-2.html