CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection

Extended Description

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.

Code Examples & CVEs

Demonstrative Examples

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.

BadOther

Register 				        Field description 				     				 				  CRITICAL_TEMP_LIMIT 				   				  [31:8] Reserved field; Read only; Default 0[7:0] Critical temp 0-255 Centigrade; Read-write-lock; Default 125 				   				   				   				  TEMP_SENSOR_CALIB 				   				  [31:0] Thermal sensor calibration data. A slope value used to map sensor reading to a degree Centigrade. Read-write; Default 25 				   				   				   				  TEMP_SENSOR_LOCK 				   				  [31:1] Reserved field; Read only; Default 0[0] Lock bit, locks CRITICAL_TEMP_LIMIT register; Write-1-once; Default 0 				   				   				   				  TEMP_HW_SHUTDOWN 				   				  [31:2] Reserved field; Read only; Default 0[1] Enable hardware shutdown on a critical temperature detection; Read-write; Default 0 				   				   				   				  CURRENT_TEMP 				   				  [31:8] Reserved field; Read only; Default 0[7:0]   Current Temp 0-255 Centigrade; Read-only; Default 0

GoodOther

Change TEMP_HW_SHUTDOWN and TEMP_SENSOR_CALIB controls to be locked by TEMP_SENSOR_LOCK. 			    			    				 				  TEMP_SENSOR_CALIB 				   				  [31:0] Thermal sensor calibration data. A slope value used to map sensor reading to a degree Centigrade. Read-write-Lock; Default 25; Locked by TEMP_SENSOR_LOCK bit[0] 				   				   				   				  TEMP_HW_SHUTDOWN 				   				  [31:2] Reserved field; Read only; Default 0[1] Enable hardware shutdown on critical temperature detection; Read-write-Lock; Default 0; Locked by TEMP_SENSOR_LOCK bit[0]

Observed CVE Examples (2)

CVE-2018-9085

Certain servers leave a write protection lock bit unset after boot, potentially allowing modification of parts of flash memory.

View Details

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].

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-1233 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-1233, Security-Sensitive Hardware Controls with Missing Lock Bit Protection, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Security-Sensitive Hardware Controls with Missing Lock Bit Protection during Architecture and Design

MITRE associates mitigation with Architecture and Design, Implementation, and Testing; documented detection approaches include Manual Analysis; recorded impacts include Modify Memory. Use these source-defined anchors to turn CWE-1233 into implementation, review, and verification checks for the affected component.

CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection — MITRE CWE

Triage CWE-1233 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-1233, Security-Sensitive Hardware Controls with Missing Lock Bit Protection, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-1233

Apply MITRE's full root-cause mapping guidance when using CWE-1233, Security-Sensitive Hardware Controls with Missing Lock Bit Protection. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-1233 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-1233, Security-Sensitive Hardware Controls with Missing Lock Bit Protection. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection?+

CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.

What are the security consequences of Security-Sensitive Hardware Controls with Missing Lock Bit Protection?+

If exploited, CWE-1233 (Security-Sensitive Hardware Controls with Missing Lock Bit Protection) it can compromise Access Control, leading to outcomes such as Modify Memory.

How do you prevent or mitigate Security-Sensitive Hardware Controls with Missing Lock Bit Protection?+

Recommended mitigations for CWE-1233 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.

How is Security-Sensitive Hardware Controls with Missing Lock Bit Protection detected?+

CWE-1233 can be detected using Manual Analysis. Combining automated tooling with manual review typically yields the best coverage.

Which programming languages are affected by Security-Sensitive Hardware Controls with Missing Lock Bit Protection?+

CWE-1233 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Security-Sensitive Hardware Controls with Missing Lock Bit Protection?+

MITRE documents real CVEs mapped to CWE-1233, including CVE-2018-9085 and CVE-2014-8273. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-1233 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.

CWE-1233: Security-Sensitive Hardware Controls with Missing Lock Bit Protection

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