CWE-925 Variante Incompleto

Improper Verification of Intent by Broadcast Receiver

This vulnerability occurs when an Android app's Broadcast Receiver accepts an Intent without confirming it originated from a trusted, authorized source, such as the operating system.

Definição

What is CWE-925?

This vulnerability occurs when an Android app's Broadcast Receiver accepts an Intent without confirming it originated from a trusted, authorized source, such as the operating system.
Android allows apps to register Broadcast Receivers for specific system-generated Intents, like a device boot completion. These are implicit intents that, by design, should only be sent by the OS. However, the same receiver registration also accepts explicit intents, which can be crafted and sent by any app on the device. A malicious app can exploit this by sending a carefully crafted explicit intent to the receiver. If the receiving app fails to verify the intent's source, it may incorrectly process the malicious intent as a legitimate system broadcast. This confusion can trigger unauthorized actions, expose sensitive data, or crash the application.
Impacto no mundo real

Real-world CVEs caused by CWE-925

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

    The following example demonstrates the weakness.

  2. 2

    The ShutdownReceiver class will handle the intent:

  3. 3

    Because the method does not confirm that the intent action is the expected system intent, any received intent will trigger the shutdown procedure, as shown here:

  4. 4

    An attacker can use this behavior to cause a denial of service.

Exemplo de código vulnerável

Vulnerable XML

The following example demonstrates the weakness.

Vulnerável XML 
<manifest package="com.example.vulnerableApplication">
  		<application>
```
...* 
  		
  		```
  				<receiver android:name=".ShutdownReceiver">
  					<intent-filter>
  						<action android:name="android.intent.action.ACTION_SHUTDOWN" />
  					</intent-filter>
  				</receiver>
```
...* 
  		
  		</application></manifest>
Payload do atacante

Because the method does not confirm that the intent action is the expected system intent, any received intent will trigger the shutdown procedure, as shown here:

Payload do atacante Java 
window.location = examplescheme://method?parameter=value
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-925

  • Architecture and Design Before acting on the Intent, check the Intent Action to make sure it matches the expected System action.
Sinais de deteção

How to detect CWE-925

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-925 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-925?

This vulnerability occurs when an Android app's Broadcast Receiver accepts an Intent without confirming it originated from a trusted, authorized source, such as the operating system.

Qual a gravidade do CWE-925?

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-925?

MITRE lists the following affected platforms: Mobile.

Como posso prevenir o CWE-925?

Before acting on the Intent, check the Intent Action to make sure it matches the expected System action.

Como é que o Plexicus deteta e corrige o CWE-925?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-925 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-925?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/925.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-925

CWE-940 Pai

Improper Verification of Source of a Communication Channel

This vulnerability occurs when an application accepts incoming communication requests without properly checking where they originate from,…

Recursos

Further reading

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