COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1234

Hardware Internal or Debug Modes Allow Override of Locks

System configuration protection may be bypassed during debug mode.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

System configuration protection may be bypassed during debug mode.

Extended description

Device configuration controls are commonly programmed after a device power reset by a trusted firmware or software module (e.g., BIOS/bootloader) and then locked from any further modification. This is commonly implemented using a trusted lock bit, which when set, disables writes to a protected set of registers or address regions. The lock protection is intended to prevent modification of certain system configuration (e.g., memory/memory protection unit configuration). If debug features supported by hardware or internal modes/system states are supported in the hardware design, modification of the lock protection may be allowed allowing access and modification of configuration information.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Bypass Protection Mechanism

Affected security scopes: Access Control

Bypass of lock bit allows access and modification of system configuration even when the lock bit is set.

Defence

How is it prevented and fixed?

Architecture and Design · Implementation · Testing

Defence to apply across several lifecycle phases

Detail
- Security Lock bit protections should be reviewed for any bypass/override modes supported. - Any supported override modes either should be removed or protected using authenticated debug modes. - Security lock programming flow and lock properties should be tested in pre-silicon and post-silicon testing.

Effectiveness: High