In GOG Galaxy 1.2.67, there is a service that is vulnerable to weak file/service permissions: GalaxyClientService.exe. An attacker can put malicious code in a Trojan horse GalaxyClientService.exe. After that, the attacker can re-start this service as an unprivileged user to escalate his/her privileges and run commands on the machine with SYSTEM rights.

An exploitable local privilege escalation vulnerability exists in the GalaxyClientService installed by GOG Galaxy. Due to Improper Access Control, an attacker can send unauthenticated local TCP packets to the service to gain SYSTEM privileges in Windows system where GOG Galaxy software is installed. All GOG Galaxy versions before 1.2.60 and all corresponding versions of GOG Galaxy 2.0 Beta are affected.