Affected: Advantech WebAccess

The BWOCXRUN.BwocxrunCtrl.1 control contains a method named “CreateProcess.” This method contains validation to ensure an attacker cannot run arbitrary command lines. After validation, the values supplied in the HTML are passed to the Windows CreateProcessA API.

The validation can be bypassed allowing for running arbitrary command lines. The command line can specify running remote files (example: UNC command line).

A function exists at offset 100019B0 of bwocxrun.ocx. Inside this function, there are 3 calls to strstr to check the contents of the user specified command line. If “\setup.exe,” “\bwvbprt.exe,” or “\bwvbprtl.exe” are contained in the command line (strstr returns nonzero value), the command line passes validation and is then passed to CreateProcessA.