CWE-1252 Detail

The CPU is not configured to provide hardware support for exclusivity of write and execute operations on memory. This allows an attacker to execute data from all of memory.

CPUs provide a special bit that supports exclusivity of write and execute operations. This bit is used to segregate areas of memory to either mark them as code (instructions, which can be executed) or data (which should not be executed). In this way, if a user can write to a region of memory, the user cannot execute from that region and vice versa. This exclusivity provided by special hardware bit is leveraged by the operating system to protect executable space. While this bit is available in most modern processors by default, in some CPUs the exclusivity is implemented via a memory-protection unit (MPU) and memory-management unit (MMU) in which memory regions can be carved out with exact read, write, and execute permissions. However, if the CPU does not have an MMU/MPU, then there is no write exclusivity. Without configuring exclusivity of operations via segregated areas of memory, an attacker may be able to inject malicious code onto memory and later execute it.

Modes Of Introduction

Architecture and Design

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Operating Systems

Class: Not OS-Specific (Undetermined)

Architectures

Class: Not Architecture-Specific (Undetermined)

Technologies

Name: Microcontroller Hardware (Undetermined)
Name: Processor Hardware (Undetermined)

Common Consequences

Potential Mitigations

Phases : Architecture and Design

Implement a dedicated bit that can be leveraged by the Operating System to mark data areas as non-executable. If such a bit is not available in the CPU, implement MMU/MPU (memory management unit / memory protection unit).

Phases : Integration

If MMU/MPU are not available, then the firewalls need to be implemented in the SoC interconnect to mimic the write-exclusivity operation.

Vulnerability Mapping Notes

Justification : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Related Attack Patterns

References

REF-1076

Cortex-R4 Manual
ARM.
https://developer.arm.com/Processors/Cortex-M4

REF-1077

MCS 51 Microcontroller Family User's Manual
Intel.
http://web.mit.edu/6.115/www/document/8051.pdf

REF-1078

Memory Protection Unit (MPU)
ARM.
https://web.archive.org/web/20200630034848/https://static.docs.arm.com/100699/0100/armv8m_architecture_memory_protection_unit_100699_0100_00_en.pdf

Submission

Modifications