Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
CWE-393 Base Rascunho
Return of Wrong Status Code
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in…
Definição
What is CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
When a system relies on these incorrect return codes to make decisions, it can lead to unpredictable application states, logic errors, and instability. For example, a function might incorrectly report a successful file deletion or a failed authentication check, causing the program flow to proceed down the wrong path.
If these status checks are part of security-critical logic—like access control, authentication, or data validation—the consequences are severe. The application might grant access to unauthorized users, assume a dangerous operation succeeded safely, or fail to alert on genuine security failures, creating hidden vulnerabilities that attackers can exploit.
Impacto no mundo real
Real-world CVEs caused by CWE-393
-
DNS server returns wrong response code for non-existent AAAA record, which effectively says that the domain is inaccessible.
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Hardware-specific implementation of system call causes incorrect results from geteuid.
-
Chain: System call returns wrong value (CWE-393), leading to a resultant NULL dereference (CWE-476).
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chain: incorrect "goto" in Apple SSL product bypasses certificate validation, allowing Adversary-in-the-Middle (AITM) attack (Apple "goto fail" bug). CWE-705 (Incorrect Control Flow Scoping) -> CWE-561 (Dead Code) -> CWE-295 (Improper Certificate Validation) -> CWE-393 (Return of Wrong Status Code) -> CWE-300 (Channel Accessible by Non-Endpoint).
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
Identificar um caminho de código que trata input não confiável sem validação.
- 2
Criar um payload que explora o comportamento inseguro — injeção, traversal, overflow ou abuso de lógica.
- 3
Entregar o payload através de um pedido normal e observar a reação da aplicação.
- 4
Iterar até que a resposta exponha dados, execute código do atacante ou escale privilégios.
Exemplo de código vulnerável
Vulnerable Java
In the following example, an HTTP 404 status code is returned in the event of an IOException encountered in a Java servlet. A 404 code is typically meant to indicate a non-existent resource and would be somewhat misleading in this case.
try {
```
// something that might throw IOException*
...} catch (IOException ioe) {
```
response.sendError(SC_NOT_FOUND);
} 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-393
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Sinais de deteção
How to detect CWE-393
O Plexicus deteta automaticamente o CWE-393 e abre um PR de correção em menos de 60 segundos.
O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.
Perguntas frequentes O que é o CWE-393?
Qual a gravidade do CWE-393?
Que linguagens ou plataformas são afetadas pelo CWE-393?
Como posso prevenir o CWE-393?
Como é que o Plexicus deteta e corrige o CWE-393?
Onde posso saber mais sobre o CWE-393?
Frequently asked questions
O que é o CWE-393?
This vulnerability occurs when a function returns an inaccurate status code or value that misrepresents the actual outcome of an operation. This false signal can cause the application to behave in unexpected and potentially insecure ways.
Qual a gravidade do CWE-393?
A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.
Que linguagens ou plataformas são afetadas pelo CWE-393?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o CWE-393?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
Como é que o Plexicus deteta e corrige o CWE-393?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-393 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-393?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/393.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-393
CWE-684 Pai
Incorrect Provision of Specified Functionality
This weakness occurs when software behaves differently than its documented specifications, which can mislead users and create security…
CWE-1245 Irmão
Improper Finite State Machines (FSMs) in Hardware Logic
This vulnerability occurs when hardware logic contains flawed Finite State Machines (FSMs). Attackers can exploit these design errors to…
CWE-392 Irmão
Missing Report of Error Condition
This vulnerability occurs when a system fails to properly signal that an error has happened. Instead of returning a clear error code,…
CWE-440 Irmão
Expected Behavior Violation
This weakness occurs when a software component, such as a function, API, or feature, fails to act as documented or intended. The system's…
CWE-446 Irmão
UI Discrepancy for Security Feature
This vulnerability occurs when a user interface incorrectly displays a security feature as active or properly configured, misleading users…
CWE-451 Irmão
User Interface (UI) Misrepresentation of Critical Information
This vulnerability occurs when a user interface fails to accurately display or highlight crucial information, potentially misleading users…
CWE-912 Irmão
Hidden Functionality
Hidden functionality refers to undocumented features, commands, or code within a product that are not part of its official specification…
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