COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1232

Improper Lock Behavior After Power State Transition

Register lock bit protection disables changes to system configuration once the bit is set. Some of the protected registers or lock bits become programmable after power state transitions (e.g., Entry and wake from low power sleep modes) causing the system configuration to be changeable.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

Register lock bit protection disables changes to system configuration once the bit is set. Some of the protected registers or lock bits become programmable after power state transitions (e.g., Entry and wake from low power sleep modes) causing the system configuration to be changeable.

Extended description

Devices may allow device configuration controls which need to be programmed after device power reset via a trusted firmware or software module (commonly set by BIOS/bootloader) and then locked from any further modification. This action is commonly implemented using a programmable lock bit, which, when set, disables writes to a protected set of registers or address regions. After a power state transition, the lock bit is set to unlocked. Some common weaknesses that can exist in such a protection scheme are that the lock gets cleared, the values of the protected registers get reset, or the lock become programmable.

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Modify Memory

Affected security scopes: Access Control

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 behavior across supported power state transitions. - Security lock programming flow and lock properties should be tested in pre-silicon and post-silicon testing including testing across power transitions.

Effectiveness: High