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 Base Brouillon
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.
Définition
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.
Impact réel
Real-world CVEs caused by CWE-242
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FTP client uses inherently insecure gets() function and is setuid root on some systems, allowing buffer overflow
Comment les attaquants l'exploitent
Parcours de l'attaquant étape par étape
- 1
The code below calls gets() to read information into a buffer.
- 2
The gets() function in C is inherently unsafe.
- 3
The code below calls the gets() function to read in data from the command line.
- 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.
Exemple de code vulnérable
Vulnerable C
The code below calls gets() to read information into a buffer.
char buf[BUFSIZE];
gets(buf); Exemple de code sécurisé
Secure 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.
Liste de contrôle de prévention
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.
Signaux de détection
How to detect CWE-242
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.
Questions fréquentes Qu'est-ce que CWE-242 ?
Quelle est la gravité de CWE-242 ?
Quels langages ou plateformes sont affectés par CWE-242 ?
Comment puis-je prévenir CWE-242 ?
Comment Plexicus détecte et corrige CWE-242 ?
Où puis-je en savoir plus sur CWE-242 ?
Frequently asked questions
Qu'est-ce que 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.
Quelle est la gravité de CWE-242 ?
MITRE évalue la probabilité d'exploitation comme Élevée — cette faiblesse est activement exploitée et doit être priorisée pour la remédiation.
Quels langages ou plateformes sont affectés par CWE-242 ?
MITRE lists the following affected platforms: C, C++.
Comment puis-je prévenir CWE-242 ?
Ban the use of dangerous functions. Use their safe equivalent. Use grep or static analysis tools to spot usage of dangerous functions.
Comment Plexicus détecte et corrige CWE-242 ?
Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-242 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.
Où puis-je en savoir plus sur CWE-242 ?
MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/242.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.
Faiblesses associées
Weaknesses related to CWE-242
CWE-1177 Parent
Use of Prohibited Code
This vulnerability occurs when software incorporates a function, library, or third-party component that has been explicitly banned by the…
CWE-676 Frère
Use of Potentially Dangerous Function
This vulnerability occurs when code calls a function that can be dangerous if misused, but can also be used safely with proper…
Ressources
Further reading
- MITRE — CWE-242 officiel https://cwe.mitre.org/data/definitions/242.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
- Writing Secure Code https://www.microsoftpressstore.com/store/writing-secure-code-9780735617223
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