An attacker with local access the to medical office computer can escalate his Windows user privileges to NT AUTHORITYSYSTEM by exploiting a race condition in the Elefant Update Service during the repair or update process. When using the repair function, the service queries the server for a list of files and their hashes. In addition, instructions to execute binaries to finalize the repair process are included. The executables are executed as NT AUTHORITYSYSTEM after they are copied over to the user writable installation folder (C:Elefant1). This means that a user can overwrite either PostESUUpdate.exe or Update_OpenJava.exe in the time frame after the copy and before the execution of the final repair step. The overwritten executable is then executed as NT AUTHORITYSYSTEM.
The product checks the state of a resource before using that resource, but the resource’s state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state.