The product uses a trusted lock bit for restricting access to registers, address regions, or other resources, but the product does not prevent the value of the lock bit from being modified after it has been set.
View on MITREIn integrated circuits and hardware intellectual property (IP) cores, 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 behavior is commonly implemented using a trusted lock bit. When set, the lock bit disables writes to a protected set of registers or address regions. Design or coding errors in the implementation of the lock bit protection feature may allow the lock bit to be modified or cleared by software after it has been set. Attackers might be able to unlock the system and features that the bit is intended to protect.
Registers protected by lock bit can be modified even when lock is set.
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.
Set the lock bit. Power cycle the device. Attempt to clear the lock bit. If the information is changed, implement a design fix. Retest. Also, attempt to indirectly clear the lock bit or bypass it.
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 firmware, and then the register needs to be locked (TEMP_SENSOR_LOCK).
In this example, note that if the system heats to critical temperature, the response of the system is controlled by the TEMP_HW_SHUTDOWN bit [1], which is not lockable. Thus, the intended security property of the critical temperature sensor cannot be fully protected, since software can misconfigure the TEMP_HW_SHUTDOWN register even after the lock bit is set to disable the shutdown response.
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 firmware, and then the register needs to be locked (TEMP_SENSOR_LOCK).
In this example, note that if the system heats to critical temperature, the response of the system is controlled by the TEMP_HW_SHUTDOWN bit [1], which is not lockable. Thus, the intended security property of the critical temperature sensor cannot be fully protected, since software can misconfigure the TEMP_HW_SHUTDOWN register even after the lock bit is set to disable the shutdown response.
The following example code is a snippet from the register locks inside the buggy OpenPiton SoC of HACK@DAC'21 [REF-1350]. Register locks help prevent SoC peripherals' registers from malicious use of resources. The registers that can potentially leak secret data are locked by register locks.
In the vulnerable code, the reglk_mem is used for locking information. If one of its bits toggle to 1, the corresponding peripheral's registers will be locked. In the context of the HACK@DAC System-on-Chip (SoC), it is pertinent to note the existence of two distinct categories of reset signals.
The following example code is a snippet from the register locks inside the buggy OpenPiton SoC of HACK@DAC'21 [REF-1350]. Register locks help prevent SoC peripherals' registers from malicious use of resources. The registers that can potentially leak secret data are locked by register locks.
In the vulnerable code, the reglk_mem is used for locking information. If one of its bits toggle to 1, the corresponding peripheral's registers will be locked. In the context of the HACK@DAC System-on-Chip (SoC), it is pertinent to note the existence of two distinct categories of reset signals.
No relationship information available for this CWE.
CWE-1231: Improper Prevention of Lock Bit Modification is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product uses a trusted lock bit for restricting access to registers, address regions, or other resources, but the product does not prevent the value of the lock bit from being modified after it has been set. In integrated circuits and hardware intellectual property (IP) cores, 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 behavior is commonly implemented using a trusted lock bit. When set, the lock bit disables writes to a protected set of registers or address regions. Design or coding errors in the implementation of the lock bit protection feature may allow the lock bit to be modified or cleared by software after it has been set. Attackers might be able to unlock the system and features that the bit is intended to protect.
If exploited, CWE-1231 (Improper Prevention of Lock Bit Modification) it can compromise Access Control, leading to outcomes such as Modify Memory.
Recommended mitigations for CWE-1231 include: 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.
CWE-1231 can be detected using Manual Analysis. Combining automated tooling with manual review typically yields the best coverage.
CWE-1231 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
MITRE documents real CVEs mapped to CWE-1231, including CVE-2017-6283. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-1231 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.