CVE-2019-17180

Valve Steam Client before 2019-09-12 allows placing or appending partially controlled filesystem content, as demonstrated by file modifications on Windows in the context of NT AUTHORITY\SYSTEM. This could lead to denial of service, elevation of privilege, or unspecified other impact.

CVE-2019-14743

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.

CVE-2019-15315

Valve Steam Client for Windows through 2019-08-16 allows privilege escalation (to NT AUTHORITY\SYSTEM) because local users can replace the current versions of SteamService.exe and SteamService.dll with older versions that lack the CVE-2019-14743 patch.

CVE-2018-12270

In Valve Steam 1528829181 BETA, it is possible to perform a homograph / homoglyph attack to create fake URLs in the client, which may trick users into visiting unintended web sites.

CVE-2019-15316

Valve Steam Client for Windows through 2019-08-20 has weak folder permissions, leading to privilege escalation (to NT AUTHORITY\SYSTEM) via crafted use of CreateMountPoint.exe and SetOpLock.exe to leverage a TOCTOU race condition.