CWE-242 Base Borrador High likelihood

Use of Inherently Dangerous Function

This vulnerability occurs when code uses functions that are inherently unsafe and cannot be reliably secured, posing a direct risk to application stability and security.

Definición

What is CWE-242?

This vulnerability occurs when code uses functions that are inherently unsafe and cannot be reliably secured, posing a direct risk to application stability and security.
Some functions are dangerous by design because they were created without security in mind, such as failing to check boundaries on user input. A classic example is the `gets()` function, which reads input without any limit on its size, allowing an attacker to overflow the destination buffer and potentially execute arbitrary code. Similarly, using the `>>` operator to read into a fixed-size character array is risky for the same reason—it doesn't validate input length, leading to buffer overflows. To prevent these issues, developers should replace these inherently dangerous functions with secure alternatives. For instance, use `fgets()` instead of `gets()` and employ methods with explicit bounds checking, like `std::string` in C++ or `scanf()` with width specifiers. Always validate and limit all external input to ensure it fits within the allocated buffer size, eliminating the root cause of these exploitable overflows.
Impacto en el mundo real

Real-world CVEs caused by CWE-242

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

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

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

  2. 2

    The gets() function in C is inherently unsafe.

  3. 3

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

  4. 4

    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.

Ejemplo de código vulnerable

Vulnerable C

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

Vulnerable C
char buf[BUFSIZE];
  gets(buf);
Ejemplo de código seguro

Secure pseudo

Seguro pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Lista de prevención

How to prevent CWE-242

  • Implementation / Requirements Ban the use of dangerous functions. Use their safe equivalent.
  • Testing Use grep or static analysis tools to spot usage of dangerous functions.
Señales de detección

How to detect CWE-242

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

CWE-242

Don't catalog this weakness. Prove it's reachable.

Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.

Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-242?

This vulnerability occurs when code uses functions that are inherently unsafe and cannot be reliably secured, posing a direct risk to application stability and security.

¿Qué gravedad tiene CWE-242?

MITRE califica la probabilidad de explotación como Alta — esta debilidad se explota activamente en la práctica y debe priorizarse para su remediación.

¿Qué lenguajes o plataformas se ven afectados por CWE-242?

MITRE lists the following affected platforms: C, C++.

¿Cómo puedo prevenir CWE-242?

Ban the use of dangerous functions. Use their safe equivalent. Use grep or static analysis tools to spot usage of dangerous functions.

¿Cómo detecta y corrige Plexicus CWE-242?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-242 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.

¿Dónde puedo aprender más sobre CWE-242?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/242.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

¿Listo para validar lo que importa?

Listo para validar lo que importa.

Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.

Calificación

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SAMPLE HANDOVER · ILLUSTRATIVE

Sample evidence handover

A trimmed view of what your team receives at the end of an AI Swarm Pentest engagement. Real engagements include full technical evidence, executive narrative, and a remediation plan.

VALIDATED FINDING Evidence attached

Server-Side Request Forgery in webhooks/receiver

demo-project/sample-app · src/webhooks/receiver.py:42

SeverityHigh CVSS 3.18.6 Priority79 Confirmedvia replay

Untrusted caller-supplied URLs reach an internal egress without an allowlist. Replayed in a sandbox against a fresh authorized target — the same control was validated to fail twice.

REVIEWER-READY REMEDIATION Merge-ready PR

Validate the target URL against an allowlist of permitted hostnames. Reject private/internal IP ranges. Enforce HTTPS only.

plexicus/remediation/webhooks-ssrf 3 changed · 0 new files
42resp = requests.get(target_url)
42+if not is_allowed_host(target_url):
43+  raise WebhookRejected(target_url)
44+resp = requests.get(target_url, timeout=5)
Every engagement hands over:
  • Executive briefing
  • Validated findings list
  • Merge-ready PRs
  • Compliance mapping (NIS2 · DORA · CRA)
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