Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.
CWE-166 Base Rascunho
Improper Handling of Missing Special Element
This vulnerability occurs when software expects a specific delimiter, terminator, or other special marker in its input but fails to properly handle situations where that element is absent. The…
Definição
What is CWE-166?
This vulnerability occurs when software expects a specific delimiter, terminator, or other special marker in its input but fails to properly handle situations where that element is absent. The application may then misinterpret boundaries, leading to crashes, data corruption, or security breaches.
Think of this like a sentence missing its period. Without the expected terminator, the software doesn't know where the input ends. It might continue reading into adjacent memory or system buffers, treating regular data as commands. This often happens when parsing structured data like strings, headers, or protocol messages where a special character defines the end of a field.
To prevent this, developers must write robust input validation that explicitly checks for the presence and correct placement of required special elements. Implement strict parsing logic with clear boundaries and use safe functions that limit read operations. Always define and handle error cases for malformed input, ensuring the system fails securely instead of proceeding with corrupted or dangerous assumptions.
Impacto no mundo real
Real-world CVEs caused by CWE-166
-
Crash via message type without separator character
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Missing special character (separator) causes crash
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HTTP GET without \r\n\r\n CRLF sequences causes product to wait indefinitely and prevents other users from accessing it
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 pseudo
A MITRE não publicou um exemplo de código para este CWE. O padrão abaixo é ilustrativo — consulte os Recursos para referências canónicas.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} 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-166
- Developers should anticipate that special elements will be removed in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
- Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Implementation Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Sinais de deteção
How to detect CWE-166
Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.
Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.
Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.
CWE-166
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-166?
Qual a gravidade do CWE-166?
Que linguagens ou plataformas são afetadas pelo CWE-166?
Como posso prevenir o CWE-166?
Como é que o Plexicus deteta e corrige o CWE-166?
Onde posso saber mais sobre o CWE-166?
Frequently asked questions
O que é o CWE-166?
This vulnerability occurs when software expects a specific delimiter, terminator, or other special marker in its input but fails to properly handle situations where that element is absent. The application may then misinterpret boundaries, leading to crashes, data corruption, or security breaches.
Qual a gravidade do CWE-166?
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-166?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o CWE-166?
Developers should anticipate that special elements will be removed in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system. Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into…
Como é que o Plexicus deteta e corrige o CWE-166?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-166 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-166?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/166.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
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