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.
| Nature | Mapping | Type | ID | Name |
|---|---|---|---|---|
| ChildOf | Discouraged | P | 284 | Improper Access Control |
| ChildOf | Allowed-with-Review | C | 667 | Improper Locking |
| Nature | Mapping | Type | ID | Name |
|---|---|---|---|---|
| MemberOf | Prohibited | C | 1199 | General Circuit and Logic Design Concerns |
| MemberOf | Prohibited | V | 1343 | Weaknesses in the 2021 CWE Most Important Hardware Weaknesses List |
| MemberOf | Prohibited | C | 1372 | ICS Supply Chain: OT Counterfeit and Malicious Corruption |
| MemberOf | Prohibited | C | 1396 | Comprehensive Categorization: Access Control |
| Nature | Mapping | Type | ID | Name |
|---|---|---|---|---|
| MemberOf | Prohibited | BS | BOSS-294 | Not Language-Specific Weaknesses |
| MemberOf | Prohibited | BS | BOSS-298 | Not OS-Specific(os class) Weaknesses |
| MemberOf | Prohibited | BS | BOSS-301 | Not Architecture-Specific (architecture class) Weaknesses |
| MemberOf | Prohibited | BS | BOSS-307 | Not Technology-Specific (technology class) Weaknesses |
| MemberOf | Prohibited | BS | BOSS-331 | Modify Memory (impact) |
| Nature | Mapping | Type | ID | Name |
|---|---|---|---|---|
| MemberOf | Prohibited | C | 1199 | General Circuit and Logic Design Concerns |
| Nature | Mapping | Type | ID | Name |
|---|---|---|---|---|
| MemberOf | Prohibited | C | 1372 | ICS Supply Chain: OT Counterfeit and Malicious Corruption |
| Scope | Likelihood | Impact | Note |
|---|---|---|---|
| Access Control | N/A | Modify Memory | System Configuration protected by the lock bit can be modified even when the lock is set. |
System Configuration protected by the lock bit can be modified even when the lock is set.
Such issues could be introduced during hardware architecture and design and identified later during Testing or System Configuration phases.
Such issues could be introduced during implementation and identified later during Testing or System Configuration phases.
Consider the example design below for a digital thermal sensor that detects overheating of the silicon and triggers system shutdown. The system critical temperature limit (CRITICAL_TEMP_LIMIT) and thermal sensor calibration (TEMP_SENSOR_CALIB) data have to be programmed by the firmware.
In this example note that only the CRITICAL_TEMP_LIMIT register is protected by the TEMP_SENSOR_LOCK bit, while the security design intent is to protect any modification of the critical temperature detection and response.
The response of the system, if the system heats to a critical temperature, is controlled by TEMP_HW_SHUTDOWN bit [1], which is not lockable. Also, the TEMP_SENSOR_CALIB register is not protected by the lock bit.
By modifying the temperature sensor calibration, the conversion of the sensor data to a degree centigrade can be changed, such that the current temperature will never be detected to exceed critical temperature value programmed by the protected lock.
Similarly, by modifying the TEMP_HW_SHUTDOWN.Enable bit, the system response detection of the current temperature exceeding critical temperature can be disabled.
| Reference | Description |
|---|---|
| CVE-2018-9085 | Certain servers leave a write protection lock bit unset after boot, potentially allowing modification of parts of flash memory. |
| CVE-2014-8273 | Chain: chipset has a race condition (CWE-362) between when an interrupt handler detects an attempt to write-enable the BIOS (in violation of the lock bit), and when the handler resets the write-enable bit back to 0, allowing attackers to issue BIOS writes during the timing window [REF-1237]. |
| Ordinality | Description |
|---|---|
| Primary | N/A |
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.
N/A
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.
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.
| Taxonomy Name | Entry ID | Fit | Entry Name |
|---|