CWE-493 Variante Rascunho High likelihood

Critical Public Variable Without Final Modifier

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

Definição

What is CWE-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.
When a critical variable—like a security flag, configuration setting, or cryptographic key—is made public without the `final` modifier, any part of the application with access to its class can alter its contents. This breaks the intended design and can lead to security failures, as other components may rely on that value remaining constant after being set. Manually tracking these exposed variables across a large codebase is challenging. An ASPM like Plexicus can automatically detect this pattern via SAST, and its AI remediation engine can suggest the specific code change—such as adding the `final` keyword or refactoring to a private field—saving significant manual review time and reducing risk.
Impacto no mundo real

Real-world CVEs caused by CWE-493

Ainda não há referências CVE públicas associadas a este CWE no catálogo da MITRE.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    Suppose this WidgetData class is used for an e-commerce web site. The programmer attempts to prevent price-tampering attacks by setting the price of the widget using the constructor.

  2. 2

    The price field is not final. Even though the value is set by the constructor, it could be modified by anybody that has access to an instance of WidgetData.

  3. 3

    Assume the following code is intended to provide the location of a configuration file that controls execution of the application.

  4. 4

    While this field is readable from any function, and thus might allow an information leak of a pathname, a more serious problem is that it can be changed by any function.

Exemplo de código vulnerável

Vulnerable Java

Suppose this WidgetData class is used for an e-commerce web site. The programmer attempts to prevent price-tampering attacks by setting the price of the widget using the constructor.

Vulnerável Java 
public final class WidgetData extends Applet {
  	public float price;
  	...
  	public WidgetData(...) {
  		this.price = LookupPrice("MyWidgetType");
  	}
  }
Exemplo de código seguro

Secure pseudo

Seguro 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-493

  • Implementation Declare all public fields as final when possible, especially if it is used to maintain internal state of an Applet or of classes used by an Applet. If a field must be public, then perform all appropriate sanity checks before accessing the field from your code.
Sinais de deteção

How to detect CWE-493

Automated Static Analysis High

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.)

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-493 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.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-493?

This vulnerability occurs when a security-sensitive variable is declared as public but not marked as final, allowing untrusted code to unexpectedly change its value after initialization.

Qual a gravidade do CWE-493?

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-493?

MITRE lists the following affected platforms: Java, C++.

Como posso prevenir o CWE-493?

Declare all public fields as final when possible, especially if it is used to maintain internal state of an Applet or of classes used by an Applet. If a field must be public, then perform all appropriate sanity checks before accessing the field from your code.

Como é que o Plexicus deteta e corrige o CWE-493?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-493 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-493?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/493.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

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Recursos

Further reading

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