Weakness · High
CWE-1252: CPU Hardware Not Configured to Support Exclusivity of Write and Execute Operations
What it is
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.
- Severity (our rating)
- High
- Likelihood of exploit
- Not rated by MITRE
- Introduced during
- Architecture and Design
- Exploited in the wild
- No CVE in CISA's catalog
In more detail
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.
What an attacker can do
- Execute Unauthorized Code or Commands (Confidentiality, Integrity)
How to prevent it
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).
Integration
- If MMU/MPU are not available, then the firewalls need to be implemented in the SoC interconnect to mimic the write-exclusivity operation.
H2 Security
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.