The ARM-based hardware debugging feature on Raspberry Pi 3 module B+ and possibly other devices allows non-secure EL1 code to read/write any EL3 (the highest privilege level in ARMv8) memory/register via inter-processor debugging. With a debug host processor A running in non-secure EL1 and a debug target processor B running in any privilege level, the debugging feature allows A to halt B and promote B to any privilege level. As a debug host, A has full control of B even if B owns a higher privilege level than A. Accordingly, A can read/write any EL3 memory/register via B. Also, with this memory access, A can execute arbitrary code in EL3.
The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
Resources such as files and directories may be inadvertently exposed through mechanisms such as insecure permissions, or when a program accidentally operates on the wrong object. For example, a program may intend that private files can only be provided to a specific user. This effectively defines a control sphere that is intended to prevent attackers from accessing these private files. If the file permissions are insecure, then parties other than the user will be able to access those files. A separate control sphere might effectively require that the user can only access the private files, but not any other files on the system. If the program does not ensure that the user is only requesting private files, then the user might be able to access other files on the system. In either case, the end result is that a resource has been exposed to the wrong party.