CWE-242: Use of Inherently Dangerous Function

Extended Description

Certain functions behave in dangerous ways regardless of how they are used. Functions in this category were often implemented without taking security concerns into account. The gets() function is unsafe because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to gets() and overflow the destination buffer. Similarly, the >> operator is unsafe to use when reading into a statically-allocated character array because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to the >> operator and overflow the destination buffer.

Code Examples & CVEs

Demonstrative Examples

The code below calls gets() to read information into a buffer.

The gets() function in C is inherently unsafe.

BadC

char buf[BUFSIZE];gets(buf);

The code below calls the gets() function to read in data from the command line.

However, gets() is inherently unsafe, because it copies all input from STDIN to the buffer without checking size. This allows the user to provide a string that is larger than the buffer size, resulting in an overflow condition.

BadC

char buf[24];printf("Please enter your name and press <Enter>\n");gets(buf);...}

Observed CVE Examples (1)

CVE-2007-4004

FTP client uses inherently insecure gets() function and is setuid root on some systems, allowing buffer overflow

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-242 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-242, Use of Inherently Dangerous Function, 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 Use of Inherently Dangerous Function during Build and Compilation

MITRE associates mitigation with Build and Compilation, Implementation, and Testing; documented detection approaches include Automated Static Analysis; recorded impacts include Varies by Context. Use these source-defined anchors to turn CWE-242 into implementation, review, and verification checks for the affected component.

CWE-242: Use of Inherently Dangerous Function — MITRE CWE

Triage CWE-242 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-242, Use of Inherently Dangerous Function, 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-242

Apply MITRE's full root-cause mapping guidance when using CWE-242, Use of Inherently Dangerous Function. 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-242 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-242, Use of Inherently Dangerous Function. 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-242: Use of Inherently Dangerous Function?+

CWE-242: Use of Inherently Dangerous Function is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product calls a function that can never be guaranteed to work safely. Certain functions behave in dangerous ways regardless of how they are used. Functions in this category were often implemented without taking security concerns into account. The gets() function is unsafe because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to gets() and overflow the destination buffer. Similarly, the >> operator is unsafe to use when reading into a statically-allocated character array because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to the >> operator and overflow the destination buffer.

What are the security consequences of Use of Inherently Dangerous Function?+

If exploited, CWE-242 (Use of Inherently Dangerous Function) it can compromise Other, leading to outcomes such as Varies by Context.

How do you prevent or mitigate Use of Inherently Dangerous Function?+

Recommended mitigations for CWE-242 include: Use grep or static analysis tools to spot usage of dangerous functions.

Which programming languages are affected by Use of Inherently Dangerous Function?+

CWE-242 commonly affects C and C++. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Use of Inherently Dangerous Function?+

MITRE documents real CVEs mapped to CWE-242, including CVE-2007-4004. 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-242 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-242: Use of Inherently Dangerous Function

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