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 Rascunho
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.
Definição
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 no mundo real
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
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 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.
Exemplo de código vulnerável
Vulnerable C
The code below calls gets() to read information into a buffer.
char buf[BUFSIZE];
gets(buf); Exemplo de código seguro
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.
Lista de verificação de prevenção
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.
Sinais de deteção
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.
Perguntas frequentes O que é o CWE-242?
Qual a gravidade do CWE-242?
Que linguagens ou plataformas são afetadas pelo CWE-242?
Como posso prevenir o CWE-242?
Como é que o Plexicus deteta e corrige o CWE-242?
Onde posso saber mais sobre o CWE-242?
Frequently asked questions
O que é o 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.
Qual a gravidade do CWE-242?
A MITRE classifica a probabilidade de exploração como Alta — esta fraqueza é ativamente explorada em campo e deve ser priorizada para remediação.
Que linguagens ou plataformas são afetadas pelo CWE-242?
MITRE lists the following affected platforms: C, C++.
Como posso prevenir o CWE-242?
Ban the use of dangerous functions. Use their safe equivalent. Use grep or static analysis tools to spot usage of dangerous functions.
Como é que o Plexicus deteta e corrige o CWE-242?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-242 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.
Onde posso saber mais sobre o CWE-242?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/242.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-242
CWE-1177 Pai
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 Irmão
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…
Recursos
Further reading
- MITRE — CWE-242 oficial 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
Pronto para validar o que importa?
Pronto para validar o que importa.
O Plexicus é Proof-Driven AppSec: achados validados, compreensão contextual e remediação revisada — ancorada em evidência, escopada com você.