In Microsoft DirectX End-User Runtime Web Installer 9.29.1974.0, a low-privilege user can replace an executable file during the installation process, which may…

In Microsoft DirectX End-User Runtime Web Installer 9.29.1974.0, a low-privilege user can replace an executable file during the installation process, which may result in unintended elevation of privileges. During installation, the installer runs with HIGH integrity and downloads executables and DLLs to the %TEMP% folder - writable by standard users. Subsequently, the installer executes the downloaded executable with HIGH integrity to complete the application installation. However, an attacker can replace the downloaded executable with a malicious, user-controlled executable. When the installer executes this replaced file, it runs the attacker's code with HIGH integrity. Since code running at HIGH integrity can escalate to SYSTEM level by registering and executing a service, this creates a complete privilege escalation chain from standard user to SYSTEM. NOTE: The Supplier disputes this record stating that they have determined this to be the behavior as designed.