CWE-1233

Base Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Stable MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE
Security-Sensitive Hardware Controls with Missing Lock Bit Protection

Description

The product uses a register lock bit protection mechanism, but it does not ensure that the lock bit prevents modification of system registers or controls that perform changes to important hardware system configuration.

Integrated circuits and hardware intellectual properties (IPs) might provide device configuration controls that need to be programmed after device power reset by a trusted firmware or software module, commonly set by BIOS/bootloader. After reset, there can be an expectation that the controls cannot be used to perform any further modification. This behavior is commonly implemented using a trusted lock bit, which can be set to disable 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). However, if the lock bit does not effectively write-protect all system registers or controls that could modify the protected system configuration, then an adversary may be able to use software to access the registers/controls and modify the protected hardware configuration.

Consequences

Access Control — Modify Memory

System Configuration protected by the lock bit can be modified even when the lock is set.

Mitigations

Phase: Architecture and Design, Implementation, Testing

Security lock bit protections must be reviewed for design inconsistency and common weaknesses. Security lock programming flow and lock properties must be tested in pre-silicon and post-silicon testing.

Detection

Manual Analysis

Set the lock bit. Attempt to modify the information protected by the lock bit. If the information is changed, implement a design fix. Retest. Also, attempt to indirectly clear the lock bit or bypass it.