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ID

CWE-926: Improper Export of Android Application Components

Weakness ID: 926
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The Android application exports a component for use by other applications, but does not properly restrict which applications can launch the component or access the data it contains.

Extended Description

The attacks and consequences of improperly exporting a component may depend on the exported component:

  • If access to an exported Activity is not restricted, any application will be able to launch the activity. This may allow a malicious application to gain access to sensitive information, modify the internal state of the application, or trick a user into interacting with the victim application while believing they are still interacting with the malicious application.

  • If access to an exported Service is not restricted, any application may start and bind to the Service. Depending on the exposed functionality, this may allow a malicious application to perform unauthorized actions, gain access to sensitive information, or corrupt the internal state of the application.

  • If access to a Content Provider is not restricted to only the expected applications, then malicious applications might be able to access the sensitive data. Note that in Android before 4.2, the Content Provider is automatically exported unless it has been explicitly declared as NOT exported.

+ Time of Introduction
  • Architecture and Design
+ Applicable Platforms

Languages

Language-independent

Architectural Paradigms

Mobile Application

+ Common Consequences
ScopeEffect
Availability
Integrity

Technical Impact: Unexpected state; DoS: crash / exit / restart; DoS: instability; Varies by context

Other applications, possibly untrusted, can launch the Activity.

Availability
Integrity

Technical Impact: Unexpected state; Gain privileges / assume identity; DoS: crash / exit / restart; DoS: instability; Varies by context

Other applications, possibly untrusted, can bind to the Service.

Confidentiality
Integrity

Technical Impact: Read application data; Modify application data

Other applications, possibly untrusted, can read or modify the data that is offered by the Content Provider.

+ Demonstrative Examples

Example 1

This application is exporting an activity and a service in its manifest.xml:

(Bad Code)
Example Language: XML 
<activity android:name="com.example.vulnerableApp.mainScreen">
...
<intent-filter>
<action android:name="com.example.vulnerableApp.OPEN_UI" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
...
</activity>
<service android:name="com.example.vulnerableApp.backgroundService">
...
<intent-filter>
<action android:name="com.example.vulnerableApp.START_BACKGROUND" />
</intent-filter>
...
</service>

Because these components have intent filters but have not explicitly set 'android:exported=false' elsewhere in the manifest, they are automatically exported so that any other application can launch them. This may lead to unintended behavior or exploits.

Example 2

This application has created a content provider to enable custom search suggestions within the application:

(Bad Code)
Example Language: XML 
<provider>
android:name="com.example.vulnerableApp.searchDB"
android:authorities="com.example.vulnerableApp.searchDB">
</provider>

Because this content provider is only intended to be used within the application, it does not need to be exported. However, in Android before 4.2, it is automatically exported thus potentially allowing malicious applications to access sensitive information.

+ Potential Mitigations

Phase: Build and Compilation

Strategy: Identify and Reduce Attack Surface

If they do not need to be shared by other applications, explicitly mark components with android:exported="false" in the application manifest.

Phase: Build and Compilation

Strategy: Identify and Reduce Attack Surface

If you only intend to use exported components between related apps under your control, use android:protectionLevel="signature" in the xml manifest to restrict access to applications signed by you.

Phases: Build and Compilation; Architecture and Design

Strategies: Identify and Reduce Attack Surface; Separation of Privilege

Limit Content Provider permissions (read/write) as appropriate.

+ Background Details

There are three types of components that can be exported in an Android application.

Activity

An Activity is an application component that provides a UI for users to interact with. A typical application will have multiple Activity screens that perform different functions, such as a main Activity screen and a separate settings Activity screen.

Service

A Service is an application component that is started by another component to execute an operation in the background, even after the invoking component is terminated. Services do not have a UI component visible to the user.

Content Provider

The Content Provider mechanism can be used to share data with other applications or internally within the same application.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class285Improper Authorization
Development Concepts (primary)699
Research Concepts (primary)1000
+ References
[REF-34] Android Open Source Project. "Security Tips". 2013-07-16. <http://developer.android.com/training/articles/security-tips.html#ContentProviders>.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
2013-07-02MITREInternal CWE Team
Modifications
Modification DateModifierOrganizationSource
2014-01-22
(Critical)
CWE Content TeamMITREInternal
Expanded entry to be more general and include all types of Android components that may be improperly exported.
2014-02-18CWE Content TeamMITREInternal
updated Background_Details, Common_Consequences, Demonstrative_Examples, Description, Maintenance_Notes, Name, Potential_Mitigations, References
Previous Entry Names
Change DatePrevious Entry Name
2014-02-18Improper Restriction of Content Provider Export to Other Applications

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Page Last Updated: May 05, 2017