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-182 Base Rascunho
Collapse of Data into Unsafe Value
This vulnerability occurs when an application's data filtering or transformation process incorrectly merges or simplifies information, producing a result that violates security rules. Essentially,…
Definição
What is CWE-182?
This vulnerability occurs when an application's data filtering or transformation process incorrectly merges or simplifies information, producing a result that violates security rules. Essentially, safe input gets collapsed into a dangerous value.
Collapse of Data into Unsafe Value happens when security checks are applied to individual pieces of data in isolation, but the process that combines or reduces this data (like trimming, canonicalizing, or aggregating) creates a new, composite value that bypasses those original checks. For example, filtering separate 'script' and 'alert' strings might pass validation, but if they are later concatenated, they form a working XSS payload. The core failure is that validation logic doesn't account for how safe components can become dangerous when merged.
Developers can prevent this by validating the final, assembled data in the exact context where it will be used, not just its individual parts. Treat any data aggregation or transformation step as a potential new input source that requires its own security evaluation. Implementing allow-list validation on the complete output string and using context-aware encoding libraries are key defensive strategies.
Impacto no mundo real
Real-world CVEs caused by CWE-182
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"/.////" in pathname collapses to absolute path.
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"/.//..//////././" is collapsed into "/.././" after ".." and "//" sequences are removed.
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".../...//" collapsed to "..." due to removal of "./" in web server.
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chain: HTTP server protects against ".." but allows "." variants such as "////./../.../". If the server removes "/.." sequences, the result would collapse into an unsafe value "////../" (CWE-182).
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MFV. Regular expression intended to protect against directory traversal reduces ".../...//" to "../".
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XSS protection mechanism strips a sequence that is nested in another sequence.
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-182
- Architecture and Design Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
- 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.
- Canonicalize the name to match that of the file system's representation of the name. This can sometimes be achieved with an available API (e.g. in Win32 the GetFullPathName function).
Sinais de deteção
How to detect CWE-182
CWE-182
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-182?
Qual a gravidade do CWE-182?
Que linguagens ou plataformas são afetadas pelo CWE-182?
Como posso prevenir o CWE-182?
Como é que o Plexicus deteta e corrige o CWE-182?
Onde posso saber mais sobre o CWE-182?
Frequently asked questions
O que é o CWE-182?
This vulnerability occurs when an application's data filtering or transformation process incorrectly merges or simplifies information, producing a result that violates security rules. Essentially, safe input gets collapsed into a dangerous value.
Qual a gravidade do CWE-182?
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-182?
A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.
Como posso prevenir o CWE-182?
Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names. 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…
Como é que o Plexicus deteta e corrige o CWE-182?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-182 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-182?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/182.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
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