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CWE-1239: Improper Zeroization of Hardware Register

Weakness ID: 1239
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The hardware product does not properly clear sensitive information from built-in registers when the user of the hardware block changes.
+ Extended Description
Hardware logic operates on data stored in registers local to the hardware block. Most hardware IPs, including cryptographic accelerators, rely on registers to buffer I/O, store intermediate values, and interface with software. The result of this is that sensitive information, such as passwords or encryption keys, can exist in locations not transparent to the user of the hardware logic. When a different entity obtains access to the IP due to a change in operating mode or conditions, the new entity can extract information belonging to the previous user if no mechanisms are in place to clear register contents. It is important to clear information stored in the hardware if a physical attack on the product is detected, or if the user of the hardware block changes. The process of clearing register contents in a hardware IP is referred to as zeroization in standards for cryptographic hardware modules such as FIPS-140-2 [REF-267].
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
ChildOfBaseBase - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.226Sensitive Information in Resource Not Removed Before Reuse
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Architecture and DesignLack of hardware mechanisms to zeroize or clear registers in the design or specification.
ImplementationMechanisms to zeroize and clear registers are in the design but implemented incorrectly.
OperationHardware-provided zeroization mechanisms are not used appropriately by the IP user (ex. firmware), or data remanence issues are not taken into account.
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.


Class: Language-Independent (Undetermined Prevalence)

Operating Systems

Class: OS-Independent (Undetermined Prevalence)


Class: Architecture-Independent (Undetermined Prevalence)


Class: System on Chip (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.


Technical Impact: Varies by Context

The consequences will depend on the information disclosed due to the vulnerability.
+ Demonstrative Examples

Example 1

Suppose a hardware IP for implementing an encryption routine works as expected, but it leaves the intermediate results in some registers that can be accessed. Exactly why this access happens is immaterial - it might be unintentional or intentional, where the designer wanted a "quick fix" for something.

+ Potential Mitigations

Phase: Architecture and Design

Every register potentially containing sensitive information must have a policy specifying how and when information is cleared, in addition to clarifying if it is the responsibility of the hardware logic or IP user to initiate the zeroization procedure at the appropriate time.
Note: Unfortunately, data disclosure can occur even after information has been overwritten/zeroized from the digital perspective. Physical characteristics of the memory can reveal the history of previously written data. For example, if the same value is written repeatedly to a memory location, the corresponding memory cells can become physically altered to a degree that even if the original data is erased it can still be recovered through physical characterization of the memory cells [REF-1055].
+ References
[REF-267] Information Technology Laboratory, National Institute of Standards and Technology. "SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2001-05-25. <>.
[REF-1055] Peter Gutmann. "Data Remanence in Semiconductor Devices". 10th USENIX Security Symposium. 2001-08. <>.
+ Content History
+ Submissions
Submission DateSubmitterOrganization
2020-02-08Nicole FernTortuga Logic
+ Modifications
Modification DateModifierOrganization
2020-08-20CWE Content TeamMITRE
updated Related_Attack_Patterns
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Page Last Updated: August 20, 2020