A data processing system and method for protecting a memory from unauthorized accesses are provided. The data processing system includes a system bus, a memory coupled to the system bus through a memory controller, and a processing core including a cache system. The memory controller is coupled to the system bus for controlling accesses to the memory that are requested by the processing core. A memory protection circuit uses one or more memory safety violation (MSV) indicators stored in out-of-bounds areas of the memory for detecting when the processing core attempts to access an out-of-bounds area of the memory. The processing core generates an error signal, such as an interrupt, when an attempt to access the out-of-bounds area is detected. The out-of-bounds area may be an unallocated area of the memory. The MSV indicator may be written to the memory by executing a flush instruction of the cache system, and may include the same number of bits as a cache line of the cache system. A data value of the MSV indicator may be a secret data value.