CWE - CWE-1242: Inclusion of Undocumented Features or Chicken Bits (4.20)
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    CWE-1242: Inclusion of Undocumented Features or Chicken Bits

    Weakness ID: 1242
    Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
    Abstraction: Base Base - 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.
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    + Description
    The device includes chicken bits or undocumented features that can create entry points for unauthorized actors.
    + Extended Description

    A common design practice is to use undocumented bits on a device that can be used to disable certain functional security features. These bits are commonly referred to as "chicken bits". They can facilitate quick identification and isolation of faulty components, features that negatively affect performance, or features that do not provide the required controllability for debug and test. Another way to achieve this is through implementation of undocumented features.

    + Common Consequences
    Section HelpThis table 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.
    Impact Details

    Modify Memory; Read Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Bypass Protection Mechanism

    		Scope: Confidentiality, Integrity, Availability, Access Control

    An attacker might exploit these interfaces for unauthorized access.
    + Potential Mitigations
    Phase(s) Mitigation

    Architecture and Design; Implementation

    The implementation of chicken bits in a released product is highly discouraged. If implemented at all, ensure that they are disabled in production devices. All interfaces to a device should be documented.

    Effectiveness: High
    + Relationships
    Section Help This table 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" (View-1000)
    Nature Type ID Name
    ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 912 Hidden Functionality
    + Relevant to the view "Hardware Design" (View-1194)
    Nature Type ID Name
    MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1198 Privilege Separation and Access Control Issues
    + Modes Of Introduction
    Section HelpThe 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.
    Phase Note
    Architecture and Design
    Implementation
    Documentation
    + Applicable Platforms
    Section HelpThis listing shows 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.
    Languages

    Class: Not Language-Specific (Undetermined Prevalence)

    Operating Systems

    Class: Not OS-Specific (Undetermined Prevalence)

    Architectures

    Class: Not Architecture-Specific (Undetermined Prevalence)

    Technologies

    Class: Not Technology-Specific (Undetermined Prevalence)

    Class: ICS/OT (Undetermined Prevalence)

    + Demonstrative Examples

    Example 1


    Consider a device that comes with various security measures, such as secure boot. The secure-boot process performs firmware-integrity verification at boot time, and this code is stored in a separate SPI-flash device. However, this code contains undocumented "special access features" intended to be used only for performing failure analysis and intended to only be unlocked by the device designer.

    (bad code)
    Example Language: Other 
    Attackers dump the code from the device and then perform reverse engineering to analyze the code. The undocumented, special-access features are identified, and attackers can activate them by sending specific commands via UART before secure-boot phase completes. Using these hidden features, attackers can perform reads and writes to memory via the UART interface. At runtime, the attackers can also execute arbitrary code and dump the entire memory contents.

    Remove all chicken bits and hidden features that are exposed to attackers. Add authorization schemes that rely on cryptographic primitives to access any features that the manufacturer does not want to expose. Clearly document all interfaces.



    + Weakness Ordinalities
    Ordinality Description
    Primary
    (where the weakness exists independent of other weaknesses)
    + Memberships
    Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
    Nature Type ID Name
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1371 ICS Supply Chain: Poorly Documented or Undocumented Features
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1396 Comprehensive Categorization: Access Control
    + Vulnerability Mapping Notes
    Usage ALLOWED
    (this CWE ID may be used to map to real-world vulnerabilities)
    Reason Acceptable-Use

    Rationale

    		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.

    Comments

    		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 Mappings
    Mapped Taxonomy Name Node ID Fit Mapped Node Name
    ISA/IEC 62443 Part 4-1 Req SD-4
    ISA/IEC 62443 Part 4-1 Req SVV-3
    ISA/IEC 62443 Part 4-2 Req CR 2.12
    + References
    [REF-1071] Ali Abbasi, Tobias Scharnowski and Thorsten Holz. "Doors of Durin: The Veiled Gate to Siemens S7 Silicon".
    <https://i.blackhat.com/eu-19/Wednesday/eu-19-Abbasi-Doors-Of-Durin-The-Veiled-Gate-To-Siemens-S7-Silicon.pdf>.
    [REF-1072] Sergei Skorobogatov and Christopher Woods. "Breakthrough Silicon Scanning Discovers Backdoor in Military Chip".
    <https://www.cl.cam.ac.uk/~sps32/Silicon_scan_draft.pdf>.
    [REF-1073] Chris Domas. "God Mode Unlocked: Hardware Backdoors in x86 CPUs".
    <https://i.blackhat.com/us-18/Thu-August-9/us-18-Domas-God-Mode-Unlocked-Hardware-Backdoors-In-x86-CPUs.pdf>.
    [REF-1074] Jonathan Brossard. "Hardware Backdooring is Practical".
    <https://media.blackhat.com/bh-us-12/Briefings/Brossard/BH_US_12_Brossard_Backdoor_Hacking_Slides.pdf>.
    [REF-1075] Sergei Skorabogatov. "Security, Reliability, and Backdoors".
    <https://www.cl.cam.ac.uk/~sps32/SG_talk_SRB.pdf>.
    + Content History
    + Submissions
    Submission Date Submitter Organization
    2020-02-13
    (CWE 4.0, 2020-02-24)     		Arun Kanuparthi, Hareesh Khattri, Parbati Kumar Manna, Narasimha Kumar V Mangipudi Intel Corporation
    + Contributions
    Contribution Date Contributor Organization
    2023-04-25 "Mapping CWE to 62443" Sub-Working Group CWE-CAPEC ICS/OT SIG
    Suggested mappings to ISA/IEC 62443.
    + Modifications
    Modification Date Modifier Organization
    2025-12-11
    (CWE 4.19, 2025-12-11)     		CWE Content Team MITRE
    updated Common_Consequences, Demonstrative_Examples, Description, Weakness_Ordinalities
    2025-04-03
    (CWE 4.17, 2025-04-03)     		CWE Content Team MITRE
    updated Relationships
    2024-02-29
    (CWE 4.14, 2024-02-29)     		CWE Content Team MITRE
    updated Taxonomy_Mappings
    2023-06-29
    (CWE 4.12, 2023-06-29)     		CWE Content Team MITRE
    updated Mapping_Notes, Taxonomy_Mappings
    2023-04-27
    (CWE 4.11, 2023-04-27)     		CWE Content Team MITRE
    updated Relationships, Taxonomy_Mappings
    2023-01-31
    (CWE 4.10, 2023-01-31)     		CWE Content Team MITRE
    updated Applicable_Platforms
    2022-04-28
    (CWE 4.7, 2022-04-28)     		CWE Content Team MITRE
    updated Relationships
    2020-08-20
    (CWE 4.2, 2020-08-20)     		CWE Content Team MITRE
    updated Applicable_Platforms, Demonstrative_Examples, Description, Potential_Mitigations, Related_Attack_Patterns
    Page Last Updated: April 30, 2026