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Improper Verification of Intent by Broadcast Receiver

Incomplete Variant
Structure: Simple
Description

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.

Extended Description

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.
Common Consequences 1
Scope: Integrity

Impact: Gain Privileges or Assume Identity

Another application can impersonate the operating system and cause the software to perform an unintended action.
Detection Methods 1
Automated Static AnalysisHigh
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.)
Potential Mitigations 1
Phase: Architecture and Design
Before acting on the Intent, check the Intent Action to make sure it matches the expected System action.
Demonstrative Examples 1
The following example demonstrates the weakness.

Code Example:

Bad
XML
xml

...*

xml
xml
The ShutdownReceiver class will handle the intent:

Code Example:

Bad
Java


...*
IntentFilter filter = new IntentFilter(Intent.ACTION_SHUTDOWN);
BroadcastReceiver sReceiver = new ShutDownReceiver();
registerReceiver(sReceiver, filter);


java


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:
Code Example:
Attack
Java
java
An attacker can use this behavior to cause a denial of service.
    
References 1
Analyzing Inter-Application Communication in Android
Erika Chin, Adrienne Porter Felt, Kate Greenwood, and David Wagner
http://www.eecs.berkeley.edu/~daw/papers/intents-mobisys11.pdf
ID: REF-922
 
  
    
 
 
Applicable Platforms 
 
 
 
 
 
Languages:
 
 
 Not Language-Specific : Undetermined 
 
 
Technologies:
 
 
 Mobile : Undetermined 
 
 
 
  
 
 
Modes of Introduction 
 
 
 
 
 
  Architecture and Design  
 
 
 
  
Related Attack Patterns 
  
Alternate Terms 
Intent Spoofing
      
 
 
Related Weaknesses 
 
 
 
 
  ChildOf:
 Improper Verification of Source of a Communication Channel (CWE-940) 
 
 
 
   
Notes 
MaintenanceThis entry will be made more comprehensive in later CWE versions.